Official Clerk JavaScript SDKs: Middleware-based route protection bypass

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

9.1 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

EPSS

• CVE-2026-41248: 0.32% estimated exploitation activity in the next 30 days; percentile 25.39 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary createRouteMatcher in @clerk/nextjs, @clerk/nuxt, and @clerk/astro can be bypassed by certain crafted requests, allowing them to skip middleware gating and reach downstream handlers. Sessions are not compromised and no existing user can be impersonated - the bypass only affects the middleware-level gating decision. Who is affected All apps using createRouteMatcher should upgrade to the patched versions. Patches are drop-in with no API changes. The information below describes the scope of the bypass and helps you understand whether you are potentially affected, but is not a reason to delay the upgrade. Apps relying only on middleware gating via createRouteMatcher are affected, because a crafted request can skip middleware checks and reach downstream handlers (API routes, server components, etc.). This middleware pattern permits the bypass: That said, the bypass is limited to the middleware-level route-matching gate. clerkMiddleware still authenticates the request and auth()…

Published by the source

16 Apr 2026, 21:28 UTC

Last modified by the source

5 May 2026, 16:26 UTC

Source last checked

26 Oct 2026, 12:51 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-vqx2-fgx2-5wq9

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-vqx2-fgx2-5wq9

3. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-vqx2-fgx2-5wq9

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# Patch Next advisory brief: CVE-2026-41248

Advisory: Official Clerk JavaScript SDKs: Middleware-based route protection bypass
IDs: CVE-2026-41248, GHSA-vqx2-fgx2-5wq9
Record: https://patchnext.com/advisories/cve-2026-41248 (revision 3, source checked 26 Oct 2026, 12:51 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: @clerk/nuxt 2.2.2, 1.13.28; @clerk/astro 3.0.15, 2.17.10, 1.5.7; @clerk/nextjs 7.2.1, 6.39.2, 5.7.6; @clerk/shared 4.8.1, 3.47.4, 2.22.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @clerk/nuxt: affected >= 1.1.0, < 1.13.28; >= 2.0.0, < 2.2.2; fixed in 2.2.2, 1.13.28
- npm @clerk/astro: affected >= 0.0.1, < 1.5.7; >= 2.0.0-snapshot.v20241206174604, <= 2.17.9; >= 3.0.0, < 3.0.15; fixed in 2.17.10, 3.0.15, 1.5.7
- npm @clerk/nextjs: affected >= 5.0.0, < 5.7.6; >= 6.0.0-snapshot.vb87a27f, < 6.39.2; >= 7.0.0, < 7.2.1; fixed in 6.39.2, 5.7.6, 7.2.1
- npm @clerk/shared: affected >= 2.20.17, < 2.22.1; >= 3.0.0-canary.v20250225091530, < 3.47.4; >= 4.0.0, < 4.8.1; fixed in 2.22.1, 3.47.4, 4.8.1

## Suggested inspection (read-only)
- `npm ls @clerk/nuxt --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.
- `npm ls @clerk/astro --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.
- `npm ls @clerk/nextjs --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.
- `npm ls @clerk/shared --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/nuxt, @clerk/astro, @clerk/nextjs, @clerk/shared.
- 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://github.com/advisories/GHSA-vqx2-fgx2-5wq9 (GitHub-reviewed advisory GHSA-vqx2-fgx2-5wq9 lists affected ranges: npm @clerk/nextjs >=5.0.0 =6.0.0-snapshot.vb87a27f =7.0.0 =1.1.0 =2.0.0 =0.0.1 =2.0.0-snapshot.v20241206174604 =3.0.0 =2.20.17 =3.0.0-canary.v20250225091530 =4.0.0 <4.8.1)
- Verified: https://osv.dev/vulnerability/GHSA-vqx2-fgx2-5wq9 (OSV record GHSA-vqx2-fgx2-5wq9 lists affected ranges: npm @clerk/nextjs >=5.0.0 =6.0.0-snapshot.vb87a27f =7.0.0 =1.1.0 =2.0.0 =0.0.1 =2.0.0-snapshot.v20241206174604 =3.0.0 =2.20.17 =3.0.0-canary.v20250225091530 =4.0.0 <4.8.1 (fixed))

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