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High, CVSS 7.4amended

Clerk: SSRF in the opt-in clerkFrontendApiProxy feature may leak secret keys to unintended host

CVE-2026-34076GHSA-gjxx-92w9-8v8f

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (@clerk/fastify 3.1.5; @clerk/express 2.0.7; @clerk/backend 3.2.3; @clerk/hono 0.1.5), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
7.4 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
EPSS
  • CVE-2026-34076: 0.32% estimated exploitation activity in the next 30 days; percentile 25.16 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Summary The clerkFrontendApiProxy function in @clerk/backend is vulnerable to Server-Side Request Forgery (SSRF). An unauthenticated attacker can craft a request path that causes the proxy to send the application's Clerk-Secret-Key to an attacker-controlled server. Affected packages Only applications that have opted into the frontendApiProxy feature are affected. This feature is not enabled by default. Users of @clerk/nextjs are not affected due to how the framework handles repeated / in request paths. | Package | Affected versions | Fixed version | |---|---|---| | @clerk/backend | = 3.0.0, <= 3.2.2 | 3.2.3 | | @clerk/express | = 2.0.0, <= 2.0.6 | 2.0.7 | | @clerk/hono | = 0.1.0, <= 0.1.4 | 0.1.5 | | @clerk/fastify | = 3.1.0, <= 3.1.4 | 3.1.5 | Search your codebase for the frontendApiProxy option. If none of the patterns below appear in your code, you are not affected. @clerk/express @clerk/hono @clerk/fastify @clerk/backend A quick way to check across your entire project: If there…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 2 · amended ·

    Amended from ghsa record GHSA-gjxx-92w9-8v8f

  2. Revision 1 · created ·

    Published from osv record GHSA-gjxx-92w9-8v8f

Agent brief

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# Patch Next advisory brief: CVE-2026-34076

Advisory: Clerk: SSRF in the opt-in clerkFrontendApiProxy feature may leak secret keys to unintended host
IDs: CVE-2026-34076, GHSA-gjxx-92w9-8v8f
Record: https://patchnext.com/advisories/cve-2026-34076 (revision 2, source checked 26 Oct 2026, 12:47 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.4)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: @clerk/fastify 3.1.5; @clerk/express 2.0.7; @clerk/backend 3.2.3; @clerk/hono 0.1.5. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @clerk/fastify: affected >= 3.1.0, <= 3.1.4; fixed in 3.1.5
- npm @clerk/express: affected >= 2.0.0, <= 2.0.6; fixed in 2.0.7
- npm @clerk/backend: affected >= 3.0.0, <= 3.2.2; fixed in 3.2.3
- npm @clerk/hono: affected >= 0.1.0, <= 0.1.4; fixed in 0.1.5

## Suggested inspection (read-only)
- `npm ls @clerk/fastify --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.
- `npm ls @clerk/express --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.
- `npm ls @clerk/backend --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.
- `npm ls @clerk/hono --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on @clerk/fastify, @clerk/express, @clerk/backend, @clerk/hono.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-gjxx-92w9-8v8f (OSV record GHSA-gjxx-92w9-8v8f lists affected ranges: npm @clerk/backend >=3.0.0 =2.0.0 =0.1.0 =3.1.0 <3.1.5 (fixed))
- Verified: https://github.com/advisories/GHSA-gjxx-92w9-8v8f (GitHub-reviewed advisory GHSA-gjxx-92w9-8v8f lists affected ranges: npm @clerk/backend >=3.0.0 =2.0.0 =0.1.0 =3.1.0 <=3.1.4)

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