fix(backend): Return TokenVerificationError from decodeJwt for undecodable tokens#9268

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Merged
wobsoriano merged 1 commit into from
Jul 30, 2026
Merged

fix(backend): Return TokenVerificationError from decodeJwt for undecodable tokens #9268

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5 changes: 5 additions & 0 deletions .changeset/decodejwt-malformed-token.md
View file
Open in desktop
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,5 @@
---
'@clerk/backend': patch
---

Return a `TokenVerificationError` from `decodeJwt` and `verifyToken` for tokens whose header, payload, or signature cannot be decoded.
13 changes: 13 additions & 0 deletions packages/backend/src/jwt/__tests__/verifyJwt.test.ts
View file
Open in desktop
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,6 @@
import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';

import { TokenVerificationError } from '../../errors';
import {
createJwt,
mockJwks,
Expand DownExpand Up@@ -85,6 +86,18 @@ describe('decodeJwt(jwt)', () => {
const { errors: [error] = [] } = decodeJwt('42');
expect(error).toMatchObject(invalidTokenError);
});

it('returns an error if the token segments are not valid base64url', () => {
const { errors: [error] = [] } = decodeJwt('aaa.bbb.ccc');
expect(error).toBeInstanceOf(TokenVerificationError);
expect(error).toMatchObject({ reason: 'token-invalid' });
});

it('returns an error if the token segments do not decode to JSON', () => {
const { errors: [error] = [] } = decodeJwt('YWJj.YWJj.YWJj');
expect(error).toBeInstanceOf(TokenVerificationError);
expect(error).toMatchObject({ reason: 'token-invalid' });
});
});

describe('verifyJwt(jwt, options)', () => {
Expand Down
19 changes: 15 additions & 4 deletions packages/backend/src/jwt/verifyJwt.ts
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -79,10 +79,21 @@ export function decodeJwt(token: string): JwtReturnType<Jwt, TokenVerificationEr
// encode - and _.

// More info at https://stackoverflow.com/questions/54062583/how-to-verify-a-signed-jwt-with-subtlecrypto-of-the-web-crypto-API
const header = JSON.parse(decoder.decode(base64url.parse(rawHeader, { loose: true })));
const payload = JSON.parse(decoder.decode(base64url.parse(rawPayload, { loose: true })));

const signature = base64url.parse(rawSignature, { loose: true });
let header, payload, signature;
try {
header = JSON.parse(decoder.decode(base64url.parse(rawHeader, { loose: true })));
payload = JSON.parse(decoder.decode(base64url.parse(rawPayload, { loose: true })));
signature = base64url.parse(rawSignature, { loose: true });
} catch {
return {
errors: [
new TokenVerificationError({
reason: TokenVerificationErrorReason.TokenInvalid,
message: `Invalid JWT form. The header, payload, or signature could not be decoded.`,
}),
],
};
}
Comment on lines +82 to +96

@coderabbitaicoderabbitaiBotJul 29, 2026

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🎯 Functional Correctness | 🟡 Minor | ⚡ Quick win

🧩 Analysis chain

🏁 Script executed:

#!/bin/bashset -euo pipefail
printf'\n== verifyJwt.ts ==\n'
sed -n '1,220p' packages/backend/src/jwt/verifyJwt.ts
printf'\n== search JWT helpers/types ==\n'
rg -n "isJwtObject|type Jwt|interface Jwt|verifyJwt|decodeJwt|TokenVerificationErrorReason" packages/backend/src/jwt packages/backend/src -g '!**/dist/**'

Repository: clerk/javascript

Length of output: 32062

🏁 Script executed:

#!/bin/bashset -euo pipefail
sed -n '1,220p' packages/backend/src/jwt/verifyJwt.ts
printf'\n---\n'
rg -n "isJwtObject|type Jwt|interface Jwt|verifyJwt|decodeJwt|TokenVerificationErrorReason" packages/backend/src/jwt packages/backend/src -g '!**/dist/**'

Repository: clerk/javascript

Length of output: 32015

🏁 Script executed:

#!/bin/bashset -euo pipefail
pwd
ls

Repository: clerk/javascript

Length of output: 517

🏁 Script executed:

#!/bin/bashset -euo pipefail
python3 - <<'PY'from pathlib import Pathp = Path('packages/backend/src/jwt/verifyJwt.ts')print(p.exists())print(p)print(p.read_text()[:4000])PY

Repository: clerk/javascript

Length of output: 4198

🏁 Script executed:

#!/bin/bashset -euo pipefail
printf'== assertions.ts ==\n'
sed -n '1,260p' packages/backend/src/jwt/assertions.ts
printf'\n== Jwt types from shared package references ==\n'
rg -n "export type Jwt|export interface Jwt|type JwtPayload|interface JwtPayload" packages -g '!**/dist/**'

Repository: clerk/javascript

Length of output: 7586

🏁 Script executed:

#!/bin/bashset -euo pipefail
printf'== assertions.ts ==\n'
sed -n '1,260p' packages/backend/src/jwt/assertions.ts
printf'\n== Jwt types search ==\n'
rg -n "export type Jwt|export interface Jwt|type JwtPayload|interface JwtPayload" packages -g '!**/dist/**'

Repository: clerk/javascript

Length of output: 7562

Reject non-object JWT parts before returning.JSON.parse can return null or a primitive here, and verifyJwt later destructures header/payload inside a catch, so tokens like bnVsbA.bnVsbA. surface a plain TypeError in errors instead of the invalid-form JWT error.

🤖 Prompt for AI Agents
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.
In `@packages/backend/src/jwt/verifyJwt.ts` around lines 82 - 96, The JWT parsing
flow in verifyJwt must validate that the decoded header and payload are non-null
objects before continuing. After JSON.parse in the try block, reject null or
primitive values using the existing Invalid JWT form TokenVerificationError
path, ensuring malformed tokens such as null parts cannot reach later
destructuring and produce a TypeError.

Sources: Coding guidelines, MCP tools


const data = {
header,
Expand Down
Loading
, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Add copy buttons to all 
 blocks\n(function() {\n function addCopyButtons() {\n document.querySelectorAll('pre code').forEach(function(codeBlock) {\n if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;\n codeBlock.parentElement.setAttribute('data-copy-added', 'true');\n \n var btn = document.createElement('button');\n btn.textContent = 'Copy';\n btn.style.cssText = 'position:absolute;top:4px;right:4px;padding:2px 8px;font-size:11px;background:#4ecdc4;border:none;border-radius:4px;color:#1a1a2e;cursor:pointer;opacity:0.7;transition:opacity 0.2s;';\n btn.onmouseover = function() { this.style.opacity = '1'; };\n btn.onmouseout = function() { this.style.opacity = '0.7'; };\n btn.onclick = function() {\n navigator.clipboard.writeText(codeBlock.textContent).then(function() {\n btn.textContent = 'Copied!';\n setTimeout(function() { btn.textContent = 'Copy'; }, 1500);\n });\n };\n codeBlock.parentElement.style.position = 'relative';\n codeBlock.parentElement.appendChild(btn);\n });\n }\n \n addCopyButtons();\n \n // Re-run on dynamic content\n var observer = new MutationObserver(addCopyButtons);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Add Copy Buttons to Code Blocks");
}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '

Skip to content
fix(backend): Return TokenVerificationError from decodeJwt for undecodable tokens#9268

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to your account

 Merged

wobsoriano
merged 1 commit into

from

Jul 30, 2026
 Merged


fix(backend): Return TokenVerificationError from decodeJwt for undecodable tokens
#9268
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5 changes: 5 additions & 0 deletions
.changeset/decodejwt-malformed-token.md

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,5 @@
---
'@clerk/backend': patch
---

Return a `TokenVerificationError` from `decodeJwt` and `verifyToken` for tokens whose header, payload, or signature cannot be decoded.

13 changes: 13 additions & 0 deletions
packages/backend/src/jwt/__tests__/verifyJwt.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,5 +1,6 @@
import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';

import { TokenVerificationError } from '../../errors';
import {
 createJwt,
 mockJwks,
Expand DownExpand Up@@ -85,6 +86,18 @@ describe('decodeJwt(jwt)', () => {
 const { errors: [error] = [] } = decodeJwt('42');
 expect(error).toMatchObject(invalidTokenError);
 });

 it('returns an error if the token segments are not valid base64url', () => {
 const { errors: [error] = [] } = decodeJwt('aaa.bbb.ccc');
 expect(error).toBeInstanceOf(TokenVerificationError);
 expect(error).toMatchObject({ reason: 'token-invalid' });
 });

 it('returns an error if the token segments do not decode to JSON', () => {
 const { errors: [error] = [] } = decodeJwt('YWJj.YWJj.YWJj');
 expect(error).toBeInstanceOf(TokenVerificationError);
 expect(error).toMatchObject({ reason: 'token-invalid' });
 });
});

describe('verifyJwt(jwt, options)', () => {
Expand Down

19 changes: 15 additions & 4 deletions
packages/backend/src/jwt/verifyJwt.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -79,10 +79,21 @@ export function decodeJwt(token: string): JwtReturnType<Jwt, TokenVerificationEr
 // encode - and _.

 // More info at https://stackoverflow.com/questions/54062583/how-to-verify-a-signed-jwt-with-subtlecrypto-of-the-web-crypto-API
 const header = JSON.parse(decoder.decode(base64url.parse(rawHeader, { loose: true })));
 const payload = JSON.parse(decoder.decode(base64url.parse(rawPayload, { loose: true })));

 const signature = base64url.parse(rawSignature, { loose: true });
 let header, payload, signature;
 try {
 header = JSON.parse(decoder.decode(base64url.parse(rawHeader, { loose: true })));
 payload = JSON.parse(decoder.decode(base64url.parse(rawPayload, { loose: true })));
 signature = base64url.parse(rawSignature, { loose: true });
 } catch {
 return {
 errors: [
 new TokenVerificationError({
 reason: TokenVerificationErrorReason.TokenInvalid,
 message: `Invalid JWT form. The header, payload, or signature could not be decoded.`,
 }),
 ],
 };
 }

Comment on lines

+82
 to 
+96

@coderabbitaicoderabbitaiBotJul 29, 2026

Copy link


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Contributor
Choose a reason for hiding this comment

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🎯 Functional Correctness | 🟡 Minor | ⚡ Quick win
🧩 Analysis chain
🏁 Script executed:
#!/bin/bashset -euo pipefail
printf'\n== verifyJwt.ts ==\n'
sed -n '1,220p' packages/backend/src/jwt/verifyJwt.ts
printf'\n== search JWT helpers/types ==\n'
rg -n "isJwtObject|type Jwt|interface Jwt|verifyJwt|decodeJwt|TokenVerificationErrorReason" packages/backend/src/jwt packages/backend/src -g '!**/dist/**'
Repository: clerk/javascript
Length of output: 32062
🏁 Script executed:
#!/bin/bashset -euo pipefail
sed -n '1,220p' packages/backend/src/jwt/verifyJwt.ts
printf'\n---\n'
rg -n "isJwtObject|type Jwt|interface Jwt|verifyJwt|decodeJwt|TokenVerificationErrorReason" packages/backend/src/jwt packages/backend/src -g '!**/dist/**'
Repository: clerk/javascript
Length of output: 32015
🏁 Script executed:
#!/bin/bashset -euo pipefail
pwd
ls
Repository: clerk/javascript
Length of output: 517
🏁 Script executed:
#!/bin/bashset -euo pipefail
python3 - <<'PY'from pathlib import Pathp = Path('packages/backend/src/jwt/verifyJwt.ts')print(p.exists())print(p)print(p.read_text()[:4000])PY
Repository: clerk/javascript
Length of output: 4198
🏁 Script executed:
#!/bin/bashset -euo pipefail
printf'== assertions.ts ==\n'
sed -n '1,260p' packages/backend/src/jwt/assertions.ts
printf'\n== Jwt types from shared package references ==\n'
rg -n "export type Jwt|export interface Jwt|type JwtPayload|interface JwtPayload" packages -g '!**/dist/**'
Repository: clerk/javascript
Length of output: 7586
🏁 Script executed:
#!/bin/bashset -euo pipefail
printf'== assertions.ts ==\n'
sed -n '1,260p' packages/backend/src/jwt/assertions.ts
printf'\n== Jwt types search ==\n'
rg -n "export type Jwt|export interface Jwt|type JwtPayload|interface JwtPayload" packages -g '!**/dist/**'
Repository: clerk/javascript
Length of output: 7562
Reject non-object JWT parts before returning.JSON.parse can return null or a primitive here, and verifyJwt later destructures header/payload inside a catch, so tokens like bnVsbA.bnVsbA. surface a plain TypeError in errors instead of the invalid-form JWT error.
🤖 Prompt for AI Agents
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.
In `@packages/backend/src/jwt/verifyJwt.ts` around lines 82 - 96, The JWT parsing
flow in verifyJwt must validate that the decoded header and payload are non-null
objects before continuing. After JSON.parse in the try block, reject null or
primitive values using the existing Invalid JWT form TokenVerificationError
path, ensuring malformed tokens such as null parts cannot reach later
destructuring and produce a TypeError.

Sources: Coding guidelines, MCP tools

 const data = {
 header,
Expand Down
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Force GitHub README to respect dark mode\n(function() {\n var style = document.createElement('style');\n style.textContent = '\n .markdown-body {\n color-scheme: dark light;\n }\n .markdown-body pre { background: #161b22 !important; }\n .markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }\n .markdown-body table th, .markdown-body table td { border-color: #30363d !important; }\n .markdown-body img { background: #0d1117; }\n .markdown-body blockquote { border-left-color: #8b949e; }\n .markdown-body hr { border-color: #30363d; }\n ';\n document.head.appendChild(style);\n})();", "GitHub Dark Mode README Fix");
}
} catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
fix(backend): Return TokenVerificationError from decodeJwt for undecodable tokens#9268

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Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

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to your account

 Merged

wobsoriano
merged 1 commit into

from

Jul 30, 2026
 Merged


fix(backend): Return TokenVerificationError from decodeJwt for undecodable tokens
#9268
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5 changes: 5 additions & 0 deletions
.changeset/decodejwt-malformed-token.md

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,5 @@
---
'@clerk/backend': patch
---

Return a `TokenVerificationError` from `decodeJwt` and `verifyToken` for tokens whose header, payload, or signature cannot be decoded.

13 changes: 13 additions & 0 deletions
packages/backend/src/jwt/__tests__/verifyJwt.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,5 +1,6 @@
import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';

import { TokenVerificationError } from '../../errors';
import {
 createJwt,
 mockJwks,
Expand DownExpand Up@@ -85,6 +86,18 @@ describe('decodeJwt(jwt)', () => {
 const { errors: [error] = [] } = decodeJwt('42');
 expect(error).toMatchObject(invalidTokenError);
 });

 it('returns an error if the token segments are not valid base64url', () => {
 const { errors: [error] = [] } = decodeJwt('aaa.bbb.ccc');
 expect(error).toBeInstanceOf(TokenVerificationError);
 expect(error).toMatchObject({ reason: 'token-invalid' });
 });

 it('returns an error if the token segments do not decode to JSON', () => {
 const { errors: [error] = [] } = decodeJwt('YWJj.YWJj.YWJj');
 expect(error).toBeInstanceOf(TokenVerificationError);
 expect(error).toMatchObject({ reason: 'token-invalid' });
 });
});

describe('verifyJwt(jwt, options)', () => {
Expand Down

19 changes: 15 additions & 4 deletions
packages/backend/src/jwt/verifyJwt.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -79,10 +79,21 @@ export function decodeJwt(token: string): JwtReturnType<Jwt, TokenVerificationEr
 // encode - and _.

 // More info at https://stackoverflow.com/questions/54062583/how-to-verify-a-signed-jwt-with-subtlecrypto-of-the-web-crypto-API
 const header = JSON.parse(decoder.decode(base64url.parse(rawHeader, { loose: true })));
 const payload = JSON.parse(decoder.decode(base64url.parse(rawPayload, { loose: true })));

 const signature = base64url.parse(rawSignature, { loose: true });
 let header, payload, signature;
 try {
 header = JSON.parse(decoder.decode(base64url.parse(rawHeader, { loose: true })));
 payload = JSON.parse(decoder.decode(base64url.parse(rawPayload, { loose: true })));
 signature = base64url.parse(rawSignature, { loose: true });
 } catch {
 return {
 errors: [
 new TokenVerificationError({
 reason: TokenVerificationErrorReason.TokenInvalid,
 message: `Invalid JWT form. The header, payload, or signature could not be decoded.`,
 }),
 ],
 };
 }

Comment on lines

+82
 to 
+96

@coderabbitaicoderabbitaiBotJul 29, 2026

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🎯 Functional Correctness | 🟡 Minor | ⚡ Quick win
🧩 Analysis chain
🏁 Script executed:
#!/bin/bashset -euo pipefail
printf'\n== verifyJwt.ts ==\n'
sed -n '1,220p' packages/backend/src/jwt/verifyJwt.ts
printf'\n== search JWT helpers/types ==\n'
rg -n "isJwtObject|type Jwt|interface Jwt|verifyJwt|decodeJwt|TokenVerificationErrorReason" packages/backend/src/jwt packages/backend/src -g '!**/dist/**'
Repository: clerk/javascript
Length of output: 32062
🏁 Script executed:
#!/bin/bashset -euo pipefail
sed -n '1,220p' packages/backend/src/jwt/verifyJwt.ts
printf'\n---\n'
rg -n "isJwtObject|type Jwt|interface Jwt|verifyJwt|decodeJwt|TokenVerificationErrorReason" packages/backend/src/jwt packages/backend/src -g '!**/dist/**'
Repository: clerk/javascript
Length of output: 32015
🏁 Script executed:
#!/bin/bashset -euo pipefail
pwd
ls
Repository: clerk/javascript
Length of output: 517
🏁 Script executed:
#!/bin/bashset -euo pipefail
python3 - <<'PY'from pathlib import Pathp = Path('packages/backend/src/jwt/verifyJwt.ts')print(p.exists())print(p)print(p.read_text()[:4000])PY
Repository: clerk/javascript
Length of output: 4198
🏁 Script executed:
#!/bin/bashset -euo pipefail
printf'== assertions.ts ==\n'
sed -n '1,260p' packages/backend/src/jwt/assertions.ts
printf'\n== Jwt types from shared package references ==\n'
rg -n "export type Jwt|export interface Jwt|type JwtPayload|interface JwtPayload" packages -g '!**/dist/**'
Repository: clerk/javascript
Length of output: 7586
🏁 Script executed:
#!/bin/bashset -euo pipefail
printf'== assertions.ts ==\n'
sed -n '1,260p' packages/backend/src/jwt/assertions.ts
printf'\n== Jwt types search ==\n'
rg -n "export type Jwt|export interface Jwt|type JwtPayload|interface JwtPayload" packages -g '!**/dist/**'
Repository: clerk/javascript
Length of output: 7562
Reject non-object JWT parts before returning.JSON.parse can return null or a primitive here, and verifyJwt later destructures header/payload inside a catch, so tokens like bnVsbA.bnVsbA. surface a plain TypeError in errors instead of the invalid-form JWT error.
🤖 Prompt for AI Agents
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.
In `@packages/backend/src/jwt/verifyJwt.ts` around lines 82 - 96, The JWT parsing
flow in verifyJwt must validate that the decoded header and payload are non-null
objects before continuing. After JSON.parse in the try block, reject null or
primitive values using the existing Invalid JWT form TokenVerificationError
path, ensuring malformed tokens such as null parts cannot reach later
destructuring and produce a TypeError.

Sources: Coding guidelines, MCP tools

 const data = {
 header,
Expand Down
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Highlight search terms from Google/DuckDuckGo/Bing referrer\n(function() {\n var ref = document.referrer;\n var terms = [];\n \n if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {\n var url = new URL(ref);\n var q = url.searchParams.get('q') || url.searchParams.get('p');\n if (q) {\n terms = q.split(/\\s+/).filter(function(t) { return t.length > 2; });\n }\n }\n \n if (terms.length === 0) return;\n \n var style = document.createElement('style');\n style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';\n document.head.appendChild(style);\n \n function highlight(node) {\n if (node.nodeType === 3) { // text node\n var text = node.textContent;\n var found = false;\n terms.forEach(function(term) {\n var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\\]\\\\]/g, '\\\\') + ')', 'gi');\n if (regex.test(text)) {\n found = true;\n var frag = document.createDocumentFragment();\n var parts = text.split(regex);\n parts.forEach(function(part, i) {\n if (i % 2 === 0) {\n frag.appendChild(document.createTextNode(part));\n } else {\n var span = document.createElement('span');\n span.className = 'userscript-highlight';\n span.textContent = part;\n frag.appendChild(span);\n }\n });\n node.parentNode.replaceChild(frag, node);\n }\n });\n } else if (node.nodeType === 1 && node.childNodes) { // element\n var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];\n if (!skipTags.includes(node.tagName)) {\n Array.from(node.childNodes).forEach(highlight);\n }\n }\n }\n \n highlight(document.body);\n \n // Re-highlight on dynamic content\n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1 || node.nodeType === 3) highlight(node);\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Highlight Search Terms");
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
fix(backend): Return TokenVerificationError from decodeJwt for undecodable tokens#9268

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

 Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and
privacy statement. We’ll occasionally send you account related emails.

Already on GitHub?
Sign in
to your account

 Merged

wobsoriano
merged 1 commit into

from

Jul 30, 2026
 Merged


fix(backend): Return TokenVerificationError from decodeJwt for undecodable tokens
#9268
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5 changes: 5 additions & 0 deletions
.changeset/decodejwt-malformed-token.md

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,5 @@
---
'@clerk/backend': patch
---

Return a `TokenVerificationError` from `decodeJwt` and `verifyToken` for tokens whose header, payload, or signature cannot be decoded.

13 changes: 13 additions & 0 deletions
packages/backend/src/jwt/__tests__/verifyJwt.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,5 +1,6 @@
import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';

import { TokenVerificationError } from '../../errors';
import {
 createJwt,
 mockJwks,
Expand DownExpand Up@@ -85,6 +86,18 @@ describe('decodeJwt(jwt)', () => {
 const { errors: [error] = [] } = decodeJwt('42');
 expect(error).toMatchObject(invalidTokenError);
 });

 it('returns an error if the token segments are not valid base64url', () => {
 const { errors: [error] = [] } = decodeJwt('aaa.bbb.ccc');
 expect(error).toBeInstanceOf(TokenVerificationError);
 expect(error).toMatchObject({ reason: 'token-invalid' });
 });

 it('returns an error if the token segments do not decode to JSON', () => {
 const { errors: [error] = [] } = decodeJwt('YWJj.YWJj.YWJj');
 expect(error).toBeInstanceOf(TokenVerificationError);
 expect(error).toMatchObject({ reason: 'token-invalid' });
 });
});

describe('verifyJwt(jwt, options)', () => {
Expand Down

19 changes: 15 additions & 4 deletions
packages/backend/src/jwt/verifyJwt.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -79,10 +79,21 @@ export function decodeJwt(token: string): JwtReturnType<Jwt, TokenVerificationEr
 // encode - and _.

 // More info at https://stackoverflow.com/questions/54062583/how-to-verify-a-signed-jwt-with-subtlecrypto-of-the-web-crypto-API
 const header = JSON.parse(decoder.decode(base64url.parse(rawHeader, { loose: true })));
 const payload = JSON.parse(decoder.decode(base64url.parse(rawPayload, { loose: true })));

 const signature = base64url.parse(rawSignature, { loose: true });
 let header, payload, signature;
 try {
 header = JSON.parse(decoder.decode(base64url.parse(rawHeader, { loose: true })));
 payload = JSON.parse(decoder.decode(base64url.parse(rawPayload, { loose: true })));
 signature = base64url.parse(rawSignature, { loose: true });
 } catch {
 return {
 errors: [
 new TokenVerificationError({
 reason: TokenVerificationErrorReason.TokenInvalid,
 message: `Invalid JWT form. The header, payload, or signature could not be decoded.`,
 }),
 ],
 };
 }

Comment on lines

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+96

@coderabbitaicoderabbitaiBotJul 29, 2026

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🎯 Functional Correctness | 🟡 Minor | ⚡ Quick win
🧩 Analysis chain
🏁 Script executed:
#!/bin/bashset -euo pipefail
printf'\n== verifyJwt.ts ==\n'
sed -n '1,220p' packages/backend/src/jwt/verifyJwt.ts
printf'\n== search JWT helpers/types ==\n'
rg -n "isJwtObject|type Jwt|interface Jwt|verifyJwt|decodeJwt|TokenVerificationErrorReason" packages/backend/src/jwt packages/backend/src -g '!**/dist/**'
Repository: clerk/javascript
Length of output: 32062
🏁 Script executed:
#!/bin/bashset -euo pipefail
sed -n '1,220p' packages/backend/src/jwt/verifyJwt.ts
printf'\n---\n'
rg -n "isJwtObject|type Jwt|interface Jwt|verifyJwt|decodeJwt|TokenVerificationErrorReason" packages/backend/src/jwt packages/backend/src -g '!**/dist/**'
Repository: clerk/javascript
Length of output: 32015
🏁 Script executed:
#!/bin/bashset -euo pipefail
pwd
ls
Repository: clerk/javascript
Length of output: 517
🏁 Script executed:
#!/bin/bashset -euo pipefail
python3 - <<'PY'from pathlib import Pathp = Path('packages/backend/src/jwt/verifyJwt.ts')print(p.exists())print(p)print(p.read_text()[:4000])PY
Repository: clerk/javascript
Length of output: 4198
🏁 Script executed:
#!/bin/bashset -euo pipefail
printf'== assertions.ts ==\n'
sed -n '1,260p' packages/backend/src/jwt/assertions.ts
printf'\n== Jwt types from shared package references ==\n'
rg -n "export type Jwt|export interface Jwt|type JwtPayload|interface JwtPayload" packages -g '!**/dist/**'
Repository: clerk/javascript
Length of output: 7586
🏁 Script executed:
#!/bin/bashset -euo pipefail
printf'== assertions.ts ==\n'
sed -n '1,260p' packages/backend/src/jwt/assertions.ts
printf'\n== Jwt types search ==\n'
rg -n "export type Jwt|export interface Jwt|type JwtPayload|interface JwtPayload" packages -g '!**/dist/**'
Repository: clerk/javascript
Length of output: 7562
Reject non-object JWT parts before returning.JSON.parse can return null or a primitive here, and verifyJwt later destructures header/payload inside a catch, so tokens like bnVsbA.bnVsbA. surface a plain TypeError in errors instead of the invalid-form JWT error.
🤖 Prompt for AI Agents
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.
In `@packages/backend/src/jwt/verifyJwt.ts` around lines 82 - 96, The JWT parsing
flow in verifyJwt must validate that the decoded header and payload are non-null
objects before continuing. After JSON.parse in the try block, reject null or
primitive values using the existing Invalid JWT form TokenVerificationError
path, ensuring malformed tokens such as null parts cannot reach later
destructuring and produce a TypeError.

Sources: Coding guidelines, MCP tools

 const data = {
 header,
Expand Down
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Strip utm_, fbclid, gclid, etc. from all links on page\n(function() {\n var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',\n 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',\n 'ref', 'ref_src', 'source', 'medium', 'campaign'];\n \n function cleanUrl(url) {\n try {\n var u = new URL(url, window.location.origin);\n var changed = false;\n trackingParams.forEach(function(p) {\n if (u.searchParams.has(p)) {\n u.searchParams.delete(p);\n changed = true;\n }\n });\n return changed ? u.toString() : url;\n } catch (e) {\n return url;\n }\n }\n \n function cleanLinks() {\n document.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n \n cleanLinks();\n \n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1) {\n if (node.tagName === 'A') cleanLinks();\n node.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Remove Tracking Parameters from Links");
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '

Skip to content
fix(backend): Return TokenVerificationError from decodeJwt for undecodable tokens#9268

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 Merged

wobsoriano
merged 1 commit into

from

Jul 30, 2026
 Merged


fix(backend): Return TokenVerificationError from decodeJwt for undecodable tokens
#9268
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5 changes: 5 additions & 0 deletions
.changeset/decodejwt-malformed-token.md

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,5 @@
---
'@clerk/backend': patch
---

Return a `TokenVerificationError` from `decodeJwt` and `verifyToken` for tokens whose header, payload, or signature cannot be decoded.

13 changes: 13 additions & 0 deletions
packages/backend/src/jwt/__tests__/verifyJwt.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,5 +1,6 @@
import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';

import { TokenVerificationError } from '../../errors';
import {
 createJwt,
 mockJwks,
Expand DownExpand Up@@ -85,6 +86,18 @@ describe('decodeJwt(jwt)', () => {
 const { errors: [error] = [] } = decodeJwt('42');
 expect(error).toMatchObject(invalidTokenError);
 });

 it('returns an error if the token segments are not valid base64url', () => {
 const { errors: [error] = [] } = decodeJwt('aaa.bbb.ccc');
 expect(error).toBeInstanceOf(TokenVerificationError);
 expect(error).toMatchObject({ reason: 'token-invalid' });
 });

 it('returns an error if the token segments do not decode to JSON', () => {
 const { errors: [error] = [] } = decodeJwt('YWJj.YWJj.YWJj');
 expect(error).toBeInstanceOf(TokenVerificationError);
 expect(error).toMatchObject({ reason: 'token-invalid' });
 });
});

describe('verifyJwt(jwt, options)', () => {
Expand Down

19 changes: 15 additions & 4 deletions
packages/backend/src/jwt/verifyJwt.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -79,10 +79,21 @@ export function decodeJwt(token: string): JwtReturnType<Jwt, TokenVerificationEr
 // encode - and _.

 // More info at https://stackoverflow.com/questions/54062583/how-to-verify-a-signed-jwt-with-subtlecrypto-of-the-web-crypto-API
 const header = JSON.parse(decoder.decode(base64url.parse(rawHeader, { loose: true })));
 const payload = JSON.parse(decoder.decode(base64url.parse(rawPayload, { loose: true })));

 const signature = base64url.parse(rawSignature, { loose: true });
 let header, payload, signature;
 try {
 header = JSON.parse(decoder.decode(base64url.parse(rawHeader, { loose: true })));
 payload = JSON.parse(decoder.decode(base64url.parse(rawPayload, { loose: true })));
 signature = base64url.parse(rawSignature, { loose: true });
 } catch {
 return {
 errors: [
 new TokenVerificationError({
 reason: TokenVerificationErrorReason.TokenInvalid,
 message: `Invalid JWT form. The header, payload, or signature could not be decoded.`,
 }),
 ],
 };
 }

Comment on lines

+82
 to 
+96

@coderabbitaicoderabbitaiBotJul 29, 2026

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Contributor
Choose a reason for hiding this comment

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🎯 Functional Correctness | 🟡 Minor | ⚡ Quick win
🧩 Analysis chain
🏁 Script executed:
#!/bin/bashset -euo pipefail
printf'\n== verifyJwt.ts ==\n'
sed -n '1,220p' packages/backend/src/jwt/verifyJwt.ts
printf'\n== search JWT helpers/types ==\n'
rg -n "isJwtObject|type Jwt|interface Jwt|verifyJwt|decodeJwt|TokenVerificationErrorReason" packages/backend/src/jwt packages/backend/src -g '!**/dist/**'
Repository: clerk/javascript
Length of output: 32062
🏁 Script executed:
#!/bin/bashset -euo pipefail
sed -n '1,220p' packages/backend/src/jwt/verifyJwt.ts
printf'\n---\n'
rg -n "isJwtObject|type Jwt|interface Jwt|verifyJwt|decodeJwt|TokenVerificationErrorReason" packages/backend/src/jwt packages/backend/src -g '!**/dist/**'
Repository: clerk/javascript
Length of output: 32015
🏁 Script executed:
#!/bin/bashset -euo pipefail
pwd
ls
Repository: clerk/javascript
Length of output: 517
🏁 Script executed:
#!/bin/bashset -euo pipefail
python3 - <<'PY'from pathlib import Pathp = Path('packages/backend/src/jwt/verifyJwt.ts')print(p.exists())print(p)print(p.read_text()[:4000])PY
Repository: clerk/javascript
Length of output: 4198
🏁 Script executed:
#!/bin/bashset -euo pipefail
printf'== assertions.ts ==\n'
sed -n '1,260p' packages/backend/src/jwt/assertions.ts
printf'\n== Jwt types from shared package references ==\n'
rg -n "export type Jwt|export interface Jwt|type JwtPayload|interface JwtPayload" packages -g '!**/dist/**'
Repository: clerk/javascript
Length of output: 7586
🏁 Script executed:
#!/bin/bashset -euo pipefail
printf'== assertions.ts ==\n'
sed -n '1,260p' packages/backend/src/jwt/assertions.ts
printf'\n== Jwt types search ==\n'
rg -n "export type Jwt|export interface Jwt|type JwtPayload|interface JwtPayload" packages -g '!**/dist/**'
Repository: clerk/javascript
Length of output: 7562
Reject non-object JWT parts before returning.JSON.parse can return null or a primitive here, and verifyJwt later destructures header/payload inside a catch, so tokens like bnVsbA.bnVsbA. surface a plain TypeError in errors instead of the invalid-form JWT error.
🤖 Prompt for AI Agents
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.
In `@packages/backend/src/jwt/verifyJwt.ts` around lines 82 - 96, The JWT parsing
flow in verifyJwt must validate that the decoded header and payload are non-null
objects before continuing. After JSON.parse in the try block, reject null or
primitive values using the existing Invalid JWT form TokenVerificationError
path, ensuring malformed tokens such as null parts cannot reach later
destructuring and produce a TypeError.

Sources: Coding guidelines, MCP tools

 const data = {
 header,
Expand Down
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Auto-enable theater mode on YouTube\n(function() {\n function tryTheater() {\n var btn = document.querySelector('button[aria-label=\"Theater mode\"], ytd-player #player button[title=\"Theater mode\"]');\n if (btn && !btn.classList.contains('activated')) {\n btn.click();\n }\n }\n \n // Try immediately\n tryTheater();\n \n // Try after navigation (SPA)\n var lastUrl = location.href;\n setInterval(function() {\n if (location.href !== lastUrl) {\n lastUrl = location.href;\n setTimeout(tryTheater, 500);\n }\n }, 1000);\n \n // Also try on player load\n var observer = new MutationObserver(tryTheater);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "YouTube Theater Mode Default");
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
fix(backend): Return TokenVerificationError from decodeJwt for undecodable tokens#9268

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

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privacy statement. We’ll occasionally send you account related emails.

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Sign in
to your account

 Merged

wobsoriano
merged 1 commit into

from

Jul 30, 2026
 Merged


fix(backend): Return TokenVerificationError from decodeJwt for undecodable tokens
#9268
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5 changes: 5 additions & 0 deletions
.changeset/decodejwt-malformed-token.md

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,5 @@
---
'@clerk/backend': patch
---

Return a `TokenVerificationError` from `decodeJwt` and `verifyToken` for tokens whose header, payload, or signature cannot be decoded.

13 changes: 13 additions & 0 deletions
packages/backend/src/jwt/__tests__/verifyJwt.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,5 +1,6 @@
import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';

import { TokenVerificationError } from '../../errors';
import {
 createJwt,
 mockJwks,
Expand DownExpand Up@@ -85,6 +86,18 @@ describe('decodeJwt(jwt)', () => {
 const { errors: [error] = [] } = decodeJwt('42');
 expect(error).toMatchObject(invalidTokenError);
 });

 it('returns an error if the token segments are not valid base64url', () => {
 const { errors: [error] = [] } = decodeJwt('aaa.bbb.ccc');
 expect(error).toBeInstanceOf(TokenVerificationError);
 expect(error).toMatchObject({ reason: 'token-invalid' });
 });

 it('returns an error if the token segments do not decode to JSON', () => {
 const { errors: [error] = [] } = decodeJwt('YWJj.YWJj.YWJj');
 expect(error).toBeInstanceOf(TokenVerificationError);
 expect(error).toMatchObject({ reason: 'token-invalid' });
 });
});

describe('verifyJwt(jwt, options)', () => {
Expand Down

19 changes: 15 additions & 4 deletions
packages/backend/src/jwt/verifyJwt.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -79,10 +79,21 @@ export function decodeJwt(token: string): JwtReturnType<Jwt, TokenVerificationEr
 // encode - and _.

 // More info at https://stackoverflow.com/questions/54062583/how-to-verify-a-signed-jwt-with-subtlecrypto-of-the-web-crypto-API
 const header = JSON.parse(decoder.decode(base64url.parse(rawHeader, { loose: true })));
 const payload = JSON.parse(decoder.decode(base64url.parse(rawPayload, { loose: true })));

 const signature = base64url.parse(rawSignature, { loose: true });
 let header, payload, signature;
 try {
 header = JSON.parse(decoder.decode(base64url.parse(rawHeader, { loose: true })));
 payload = JSON.parse(decoder.decode(base64url.parse(rawPayload, { loose: true })));
 signature = base64url.parse(rawSignature, { loose: true });
 } catch {
 return {
 errors: [
 new TokenVerificationError({
 reason: TokenVerificationErrorReason.TokenInvalid,
 message: `Invalid JWT form. The header, payload, or signature could not be decoded.`,
 }),
 ],
 };
 }

Comment on lines

+82
 to 
+96

@coderabbitaicoderabbitaiBotJul 29, 2026

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🎯 Functional Correctness | 🟡 Minor | ⚡ Quick win
🧩 Analysis chain
🏁 Script executed:
#!/bin/bashset -euo pipefail
printf'\n== verifyJwt.ts ==\n'
sed -n '1,220p' packages/backend/src/jwt/verifyJwt.ts
printf'\n== search JWT helpers/types ==\n'
rg -n "isJwtObject|type Jwt|interface Jwt|verifyJwt|decodeJwt|TokenVerificationErrorReason" packages/backend/src/jwt packages/backend/src -g '!**/dist/**'
Repository: clerk/javascript
Length of output: 32062
🏁 Script executed:
#!/bin/bashset -euo pipefail
sed -n '1,220p' packages/backend/src/jwt/verifyJwt.ts
printf'\n---\n'
rg -n "isJwtObject|type Jwt|interface Jwt|verifyJwt|decodeJwt|TokenVerificationErrorReason" packages/backend/src/jwt packages/backend/src -g '!**/dist/**'
Repository: clerk/javascript
Length of output: 32015
🏁 Script executed:
#!/bin/bashset -euo pipefail
pwd
ls
Repository: clerk/javascript
Length of output: 517
🏁 Script executed:
#!/bin/bashset -euo pipefail
python3 - <<'PY'from pathlib import Pathp = Path('packages/backend/src/jwt/verifyJwt.ts')print(p.exists())print(p)print(p.read_text()[:4000])PY
Repository: clerk/javascript
Length of output: 4198
🏁 Script executed:
#!/bin/bashset -euo pipefail
printf'== assertions.ts ==\n'
sed -n '1,260p' packages/backend/src/jwt/assertions.ts
printf'\n== Jwt types from shared package references ==\n'
rg -n "export type Jwt|export interface Jwt|type JwtPayload|interface JwtPayload" packages -g '!**/dist/**'
Repository: clerk/javascript
Length of output: 7586
🏁 Script executed:
#!/bin/bashset -euo pipefail
printf'== assertions.ts ==\n'
sed -n '1,260p' packages/backend/src/jwt/assertions.ts
printf'\n== Jwt types search ==\n'
rg -n "export type Jwt|export interface Jwt|type JwtPayload|interface JwtPayload" packages -g '!**/dist/**'
Repository: clerk/javascript
Length of output: 7562
Reject non-object JWT parts before returning.JSON.parse can return null or a primitive here, and verifyJwt later destructures header/payload inside a catch, so tokens like bnVsbA.bnVsbA. surface a plain TypeError in errors instead of the invalid-form JWT error.
🤖 Prompt for AI Agents
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.
In `@packages/backend/src/jwt/verifyJwt.ts` around lines 82 - 96, The JWT parsing
flow in verifyJwt must validate that the decoded header and payload are non-null
objects before continuing. After JSON.parse in the try block, reject null or
primitive values using the existing Invalid JWT form TokenVerificationError
path, ensuring malformed tokens such as null parts cannot reach later
destructuring and produce a TypeError.

Sources: Coding guidelines, MCP tools

 const data = {
 header,
Expand Down
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Remove or un-stick sticky/fixed headers that block content\n(function() {\n function unstick() {\n document.querySelectorAll('header, nav, [role=\"banner\"], .header, .navbar, .sticky, .fixed-top, [style*=\"position: fixed\"], [style*=\"position:sticky\"]').forEach(function(el) {\n if (el.style.position === 'fixed' || el.style.position === 'sticky' || \n getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {\n el.style.position = 'static';\n el.style.top = 'auto';\n el.style.zIndex = 'auto';\n }\n });\n }\n \n unstick();\n \n var observer = new MutationObserver(unstick);\n observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });\n})();", "Kill Sticky Headers");
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
fix(backend): Return TokenVerificationError from decodeJwt for undecodable tokens#9268

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

 Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and
privacy statement. We’ll occasionally send you account related emails.

Already on GitHub?
Sign in
to your account

 Merged

wobsoriano
merged 1 commit into

from

Jul 30, 2026
 Merged


fix(backend): Return TokenVerificationError from decodeJwt for undecodable tokens
#9268
Show file tree
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5 changes: 5 additions & 0 deletions
.changeset/decodejwt-malformed-token.md

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,5 @@
---
'@clerk/backend': patch
---

Return a `TokenVerificationError` from `decodeJwt` and `verifyToken` for tokens whose header, payload, or signature cannot be decoded.

13 changes: 13 additions & 0 deletions
packages/backend/src/jwt/__tests__/verifyJwt.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,5 +1,6 @@
import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';

import { TokenVerificationError } from '../../errors';
import {
 createJwt,
 mockJwks,
Expand DownExpand Up@@ -85,6 +86,18 @@ describe('decodeJwt(jwt)', () => {
 const { errors: [error] = [] } = decodeJwt('42');
 expect(error).toMatchObject(invalidTokenError);
 });

 it('returns an error if the token segments are not valid base64url', () => {
 const { errors: [error] = [] } = decodeJwt('aaa.bbb.ccc');
 expect(error).toBeInstanceOf(TokenVerificationError);
 expect(error).toMatchObject({ reason: 'token-invalid' });
 });

 it('returns an error if the token segments do not decode to JSON', () => {
 const { errors: [error] = [] } = decodeJwt('YWJj.YWJj.YWJj');
 expect(error).toBeInstanceOf(TokenVerificationError);
 expect(error).toMatchObject({ reason: 'token-invalid' });
 });
});

describe('verifyJwt(jwt, options)', () => {
Expand Down

19 changes: 15 additions & 4 deletions
packages/backend/src/jwt/verifyJwt.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -79,10 +79,21 @@ export function decodeJwt(token: string): JwtReturnType<Jwt, TokenVerificationEr
 // encode - and _.

 // More info at https://stackoverflow.com/questions/54062583/how-to-verify-a-signed-jwt-with-subtlecrypto-of-the-web-crypto-API
 const header = JSON.parse(decoder.decode(base64url.parse(rawHeader, { loose: true })));
 const payload = JSON.parse(decoder.decode(base64url.parse(rawPayload, { loose: true })));

 const signature = base64url.parse(rawSignature, { loose: true });
 let header, payload, signature;
 try {
 header = JSON.parse(decoder.decode(base64url.parse(rawHeader, { loose: true })));
 payload = JSON.parse(decoder.decode(base64url.parse(rawPayload, { loose: true })));
 signature = base64url.parse(rawSignature, { loose: true });
 } catch {
 return {
 errors: [
 new TokenVerificationError({
 reason: TokenVerificationErrorReason.TokenInvalid,
 message: `Invalid JWT form. The header, payload, or signature could not be decoded.`,
 }),
 ],
 };
 }

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+96

@coderabbitaicoderabbitaiBotJul 29, 2026

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🎯 Functional Correctness | 🟡 Minor | ⚡ Quick win
🧩 Analysis chain
🏁 Script executed:
#!/bin/bashset -euo pipefail
printf'\n== verifyJwt.ts ==\n'
sed -n '1,220p' packages/backend/src/jwt/verifyJwt.ts
printf'\n== search JWT helpers/types ==\n'
rg -n "isJwtObject|type Jwt|interface Jwt|verifyJwt|decodeJwt|TokenVerificationErrorReason" packages/backend/src/jwt packages/backend/src -g '!**/dist/**'
Repository: clerk/javascript
Length of output: 32062
🏁 Script executed:
#!/bin/bashset -euo pipefail
sed -n '1,220p' packages/backend/src/jwt/verifyJwt.ts
printf'\n---\n'
rg -n "isJwtObject|type Jwt|interface Jwt|verifyJwt|decodeJwt|TokenVerificationErrorReason" packages/backend/src/jwt packages/backend/src -g '!**/dist/**'
Repository: clerk/javascript
Length of output: 32015
🏁 Script executed:
#!/bin/bashset -euo pipefail
pwd
ls
Repository: clerk/javascript
Length of output: 517
🏁 Script executed:
#!/bin/bashset -euo pipefail
python3 - <<'PY'from pathlib import Pathp = Path('packages/backend/src/jwt/verifyJwt.ts')print(p.exists())print(p)print(p.read_text()[:4000])PY
Repository: clerk/javascript
Length of output: 4198
🏁 Script executed:
#!/bin/bashset -euo pipefail
printf'== assertions.ts ==\n'
sed -n '1,260p' packages/backend/src/jwt/assertions.ts
printf'\n== Jwt types from shared package references ==\n'
rg -n "export type Jwt|export interface Jwt|type JwtPayload|interface JwtPayload" packages -g '!**/dist/**'
Repository: clerk/javascript
Length of output: 7586
🏁 Script executed:
#!/bin/bashset -euo pipefail
printf'== assertions.ts ==\n'
sed -n '1,260p' packages/backend/src/jwt/assertions.ts
printf'\n== Jwt types search ==\n'
rg -n "export type Jwt|export interface Jwt|type JwtPayload|interface JwtPayload" packages -g '!**/dist/**'
Repository: clerk/javascript
Length of output: 7562
Reject non-object JWT parts before returning.JSON.parse can return null or a primitive here, and verifyJwt later destructures header/payload inside a catch, so tokens like bnVsbA.bnVsbA. surface a plain TypeError in errors instead of the invalid-form JWT error.
🤖 Prompt for AI Agents
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.
In `@packages/backend/src/jwt/verifyJwt.ts` around lines 82 - 96, The JWT parsing
flow in verifyJwt must validate that the decoded header and payload are non-null
objects before continuing. After JSON.parse in the try block, reject null or
primitive values using the existing Invalid JWT form TokenVerificationError
path, ensuring malformed tokens such as null parts cannot reach later
destructuring and produce a TypeError.

Sources: Coding guidelines, MCP tools

 const data = {
 header,
Expand Down
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Universal Dark Mode - works on any site\n(function() {\n var enabled = true;\n \n function applyDarkMode() {\n if (!enabled) return;\n \n // Create style element if it doesn't exist\n var style = document.getElementById('universal-dark-mode-style');\n if (!style) {\n style = document.createElement('style');\n style.id = 'universal-dark-mode-style';\n document.head.appendChild(style);\n }\n \n // Dark mode CSS - inverts colors but preserves images/video\n style.textContent = '\n /* Invert everything except media */\n html {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #1a1a2e !important;\n }\n \n /* Restore images, videos, iframes, canvas */\n img, video, iframe, canvas, svg, picture, [style*=\"background-image\"] {\n filter: invert(1) hue-rotate(180deg) !important;\n }\n \n /* Preserve specific elements that should not be inverted */\n .no-dark-mode, .no-dark-mode *,\n [data-theme=\"light\"], [data-theme=\"light\"],\n .ace_editor, .ace_editor *,\n .CodeMirror, .CodeMirror *,\n .monaco-editor, .monaco-editor *,\n .markdown-body pre, .markdown-body pre *,\n .highlight, .highlight *,\n pre code, pre code * {\n filter: none !important;\n }\n \n /* Fix common UI elements */\n .modal, .popup, .dropdown-menu, .tooltip, .popover {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #2d2d44 !important;\n border-color: #444 !important;\n }\n \n /* Scrollbars */\n ::-webkit-scrollbar { background: #1a1a2e !important; }\n ::-webkit-scrollbar-thumb { background: #444 !important; }\n ::-webkit-scrollbar-thumb:hover { background: #555 !important; }\n \n /* Selection */\n ::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ';\n }\n \n function removeDarkMode() {\n var style = document.getElementById('universal-dark-mode-style');\n if (style) style.remove();\n }\n \n // Toggle with Alt+Shift+D\n document.addEventListener('keydown', function(e) {\n if (e.altKey && e.shiftKey && e.key === 'D') {\n e.preventDefault();\n enabled = !enabled;\n if (enabled) {\n applyDarkMode();\n console.log('[Universal Dark Mode] Enabled');\n } else {\n removeDarkMode();\n console.log('[Universal Dark Mode] Disabled');\n }\n }\n });\n \n // Apply on load\n applyDarkMode();\n \n // Re-apply on dynamic content\n var observer = new MutationObserver(function(mutations) {\n if (enabled && !document.getElementById('universal-dark-mode-style')) {\n applyDarkMode();\n }\n });\n observer.observe(document.head, { childList: true });\n \n console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');\n})();", "Universal Dark Mode");
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();

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fix(backend): Return TokenVerificationError from decodeJwt for undecodable tokens#9268

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 Merged

wobsoriano
merged 1 commit into

from

Jul 30, 2026
 Merged


fix(backend): Return TokenVerificationError from decodeJwt for undecodable tokens
#9268
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5 changes: 5 additions & 0 deletions
.changeset/decodejwt-malformed-token.md

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,5 @@
---
'@clerk/backend': patch
---

Return a `TokenVerificationError` from `decodeJwt` and `verifyToken` for tokens whose header, payload, or signature cannot be decoded.

13 changes: 13 additions & 0 deletions
packages/backend/src/jwt/__tests__/verifyJwt.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,5 +1,6 @@
import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';

import { TokenVerificationError } from '../../errors';
import {
 createJwt,
 mockJwks,
Expand DownExpand Up@@ -85,6 +86,18 @@ describe('decodeJwt(jwt)', () => {
 const { errors: [error] = [] } = decodeJwt('42');
 expect(error).toMatchObject(invalidTokenError);
 });

 it('returns an error if the token segments are not valid base64url', () => {
 const { errors: [error] = [] } = decodeJwt('aaa.bbb.ccc');
 expect(error).toBeInstanceOf(TokenVerificationError);
 expect(error).toMatchObject({ reason: 'token-invalid' });
 });

 it('returns an error if the token segments do not decode to JSON', () => {
 const { errors: [error] = [] } = decodeJwt('YWJj.YWJj.YWJj');
 expect(error).toBeInstanceOf(TokenVerificationError);
 expect(error).toMatchObject({ reason: 'token-invalid' });
 });
});

describe('verifyJwt(jwt, options)', () => {
Expand Down

19 changes: 15 additions & 4 deletions
packages/backend/src/jwt/verifyJwt.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -79,10 +79,21 @@ export function decodeJwt(token: string): JwtReturnType<Jwt, TokenVerificationEr
 // encode - and _.

 // More info at https://stackoverflow.com/questions/54062583/how-to-verify-a-signed-jwt-with-subtlecrypto-of-the-web-crypto-API
 const header = JSON.parse(decoder.decode(base64url.parse(rawHeader, { loose: true })));
 const payload = JSON.parse(decoder.decode(base64url.parse(rawPayload, { loose: true })));

 const signature = base64url.parse(rawSignature, { loose: true });
 let header, payload, signature;
 try {
 header = JSON.parse(decoder.decode(base64url.parse(rawHeader, { loose: true })));
 payload = JSON.parse(decoder.decode(base64url.parse(rawPayload, { loose: true })));
 signature = base64url.parse(rawSignature, { loose: true });
 } catch {
 return {
 errors: [
 new TokenVerificationError({
 reason: TokenVerificationErrorReason.TokenInvalid,
 message: `Invalid JWT form. The header, payload, or signature could not be decoded.`,
 }),
 ],
 };
 }

Comment on lines

+82
 to 
+96

@coderabbitaicoderabbitaiBotJul 29, 2026

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🎯 Functional Correctness | 🟡 Minor | ⚡ Quick win
🧩 Analysis chain
🏁 Script executed:
#!/bin/bashset -euo pipefail
printf'\n== verifyJwt.ts ==\n'
sed -n '1,220p' packages/backend/src/jwt/verifyJwt.ts
printf'\n== search JWT helpers/types ==\n'
rg -n "isJwtObject|type Jwt|interface Jwt|verifyJwt|decodeJwt|TokenVerificationErrorReason" packages/backend/src/jwt packages/backend/src -g '!**/dist/**'
Repository: clerk/javascript
Length of output: 32062
🏁 Script executed:
#!/bin/bashset -euo pipefail
sed -n '1,220p' packages/backend/src/jwt/verifyJwt.ts
printf'\n---\n'
rg -n "isJwtObject|type Jwt|interface Jwt|verifyJwt|decodeJwt|TokenVerificationErrorReason" packages/backend/src/jwt packages/backend/src -g '!**/dist/**'
Repository: clerk/javascript
Length of output: 32015
🏁 Script executed:
#!/bin/bashset -euo pipefail
pwd
ls
Repository: clerk/javascript
Length of output: 517
🏁 Script executed:
#!/bin/bashset -euo pipefail
python3 - <<'PY'from pathlib import Pathp = Path('packages/backend/src/jwt/verifyJwt.ts')print(p.exists())print(p)print(p.read_text()[:4000])PY
Repository: clerk/javascript
Length of output: 4198
🏁 Script executed:
#!/bin/bashset -euo pipefail
printf'== assertions.ts ==\n'
sed -n '1,260p' packages/backend/src/jwt/assertions.ts
printf'\n== Jwt types from shared package references ==\n'
rg -n "export type Jwt|export interface Jwt|type JwtPayload|interface JwtPayload" packages -g '!**/dist/**'
Repository: clerk/javascript
Length of output: 7586
🏁 Script executed:
#!/bin/bashset -euo pipefail
printf'== assertions.ts ==\n'
sed -n '1,260p' packages/backend/src/jwt/assertions.ts
printf'\n== Jwt types search ==\n'
rg -n "export type Jwt|export interface Jwt|type JwtPayload|interface JwtPayload" packages -g '!**/dist/**'
Repository: clerk/javascript
Length of output: 7562
Reject non-object JWT parts before returning.JSON.parse can return null or a primitive here, and verifyJwt later destructures header/payload inside a catch, so tokens like bnVsbA.bnVsbA. surface a plain TypeError in errors instead of the invalid-form JWT error.
🤖 Prompt for AI Agents
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.
In `@packages/backend/src/jwt/verifyJwt.ts` around lines 82 - 96, The JWT parsing
flow in verifyJwt must validate that the decoded header and payload are non-null
objects before continuing. After JSON.parse in the try block, reject null or
primitive values using the existing Invalid JWT form TokenVerificationError
path, ensuring malformed tokens such as null parts cannot reach later
destructuring and produce a TypeError.

Sources: Coding guidelines, MCP tools

 const data = {
 header,
Expand Down
Loading