Security Digest · Vulnerability record
CVE-2026-41248: Official Clerk JavaScript SDKs: Middleware-based route protection bypass
Clerk JavaScript is the official JavaScript repository for Clerk authentication.
CVSS 9.1 Critical EPSS 0.5% · p44
Should you act?
Critical and remotely reachable
No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.
- No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
- EPSS 0.5%, percentile 44: FIRST’s model estimates a 0.5% chance of exploitation activity in the next 30 days, higher than 44% of all scored CVEs (low). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes
@clerk/nextjs(npm) >= 5.0.0, < 5.7.6, fixed in 5.7.6;@clerk/nuxt(npm) >= 1.1.0, < 1.13.28, fixed in 1.13.28;@clerk/astro(npm) >= 0.0.1, < 1.5.7, fixed in 1.5.7;@clerk/shared(npm) >= 2.20.17, < 2.22.1, fixed in 2.22.1. Check your lockfile, including transitive dependencies.
What it is
Clerk JavaScript is the official JavaScript repository for Clerk authentication. 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. This vulnerability is fixed in @clerk/astro 1.5.7, 2.17.10, and 3.0.15; @clerk/nextjs 5.7.6, 6.39.2, and 7.2.1; @clerk/nuxt 1.13.28 and 2.2.2; and @clerk/shared 2.22.1, 3.47.4, anc 4.8.1
From the GitHub advisory
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.
Weakness type: CWE-436, CWE-863.
Product: @clerk/nextjs (npm) · Assigned by: GitHub_M · Published: 2026-04-24
Affected and fixed versions
| Ecosystem | Package | Vulnerable | First fixed |
|---|---|---|---|
| npm | @clerk/nextjs | >= 5.0.0, < 5.7.6 | 5.7.6 |
| npm | @clerk/nuxt | >= 1.1.0, < 1.13.28 | 1.13.28 |
| npm | @clerk/astro | >= 0.0.1, < 1.5.7 | 1.5.7 |
| npm | @clerk/shared | >= 2.20.17, < 2.22.1 | 2.22.1 |
| npm | @clerk/nextjs | >= 6.0.0-snapshot.vb87a27f, < 6.39.2 | 6.39.2 |
| npm | @clerk/nextjs | >= 7.0.0, < 7.2.1 | 7.2.1 |
| npm | @clerk/nuxt | >= 2.0.0, < 2.2.2 | 2.2.2 |
| npm | @clerk/astro | >= 2.0.0-snapshot.v20241206174604, <= 2.17.9 | 2.17.10 |
| npm | @clerk/astro | >= 3.0.0, < 3.0.15 | 3.0.15 |
| npm | @clerk/shared | >= 3.0.0-canary.v20250225091530, < 3.47.4 | 3.47.4 |
| npm | @clerk/shared | >= 4.0.0, < 4.8.1 | 4.8.1 |
| Vendor | Product | Affected versions (per CVE record) |
|---|---|---|
| clerk | astro | >= 0.0.1, < 1.5.7, >= 2.0.0-snapshot.v20241206174604, <= 2.17.9, >= 3.0.0, < 3.0.15 |
| clerk | nextjs | >= 5.0.0, < 5.7.6, >= 6.0.0-snapshot.vb87a27f, < 6.39.2, >= 7.0.0, < 7.2.1 |
| clerk | nuxt | >= 1.1.0, < 1.13.28, >= 2.0.0, < 2.2.2 |
| clerk | shared | >= 2.20.17, < 2.22.1, >= 3.0.0-canary.v20250225091530, < 3.47.4, >= 4.0.0, < 4.8.1 |
Severity scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_M | 3.1 | 9.1 Critical | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N |
| GitHub | 3.1 | 9.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N |
- Attack vector: network (remotely reachable)
- Attack complexity: low
- Privileges required: none (no login)
- User interaction: none
- Scope: unchanged
CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.
Exploitation and urgency
- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation none, automatable no, technical impact total.
- FIRST EPSS (model of 2026-10-21): 0.53% probability of exploitation activity in the next 30 days; percentile 44.
Timeline
- — GitHub-reviewed advisory GHSA-vqx2-fgx2-5wq9 published (critical)
- — CVE record published by GitHub_M
- — CVE record last updated
Sources and references
Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.
Vulnerability records
- GitHub Advisory GHSA-vqx2-fgx2-5wq9 github.com
- CVE.org record CVE-2026-41248 cve.org
- NVD entry CVE-2026-41248 nvd.nist.gov
Other references from the CVE record and advisory
- github.com github.com