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@clerk/backend: Webhook verification vulnerability

High
brkalow published GHSA-9mp4-77wg-rwx9 Jul 9, 2025

Package

npm @clerk/astro (npm)

Affected versions

>= 2.9.0 < 2.10.2

Patched versions

2.10.2
npm @clerk/backend (npm)
>= 2.0.0 < 2.4.0
2.4.0
npm @clerk/express (npm)
>= 1.6.0 < 1.7.4
1.7.4
npm @clerk/fastify (npm)
>= 2.3.0 < 2.4.4
2.4.4
npm @clerk/nextjs (npm)
>= 6.2.10 < 6.23.3
6.23.3
npm @clerk/nuxt (npm)
>= 1.7.0 < 1.7.5
1.7.5
npm @clerk/react-router (npm)
>= 1.5.0 < 1.6.4
1.6.4
npm @clerk/remix (npm)
>= 4.8.0 < 4.8.5
4.8.5
npm @clerk/tanstack-react-start (npm)
>= 0.16.0 < 0.18.3
0.18.3

Description

Impact

Applications that use the verifyWebhook() helper to verify incoming Clerk webhooks are susceptible to accepting improperly signed webhook events.

Patches

  • @clerk/backend: the helper has been patched as of 2.4.0
  • @clerk/astro: the helper has been patched as of 2.10.2
  • @clerk/express: the helper has been patched as of 1.7.4
  • @clerk/fastify: the helper has been patched as of 2.4.4
  • @clerk/nextjs: the helper has been patched as of 6.23.3
  • @clerk/nuxt: the helper has been patched as of 1.7.5
  • @clerk/react-router: the helper has been patched as of 1.6.4
  • @clerk/remix: the helper has been patched as of 4.8.5
  • @clerk/tanstack-react-start: the helper has been patched as of 0.18.3

Resolution

The issue was resolved in @clerk/backend 2.4.0 by:

  • Properly parsing the webhook request's signatures and comparing them against the signature generated from the received event

Workarounds

If unable to upgrade, developers can workaround this issue by verifying webhooks manually, per this documentation.

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

CVE ID

CVE-2025-53548

Weaknesses

Insufficient Verification of Data Authenticity

The product does not sufficiently verify the origin or authenticity of data, in a way that causes it to accept invalid data. Learn more on MITRE.

Credits