What is CVE-2026-42349?

CVE-2026-42349 is a high-severity vulnerability in @Clerk Astro, classified under Improper Check for Unusual or Exceptional Conditions. CVSS score: 8.1/10. Published 2026-05-11.

How severe is CVE-2026-42349?

High severity. CVSS v3 base score is 8.1 out of 10.

Auth bypass in @Clerk Astro

CVE-2026-42349

Clerk JavaScript is the official JavaScript repository for Clerk authentication. has(), auth.protect(), and related authorization predicates in @clerk/shared, @clerk/nextjs, @clerk/backend, and other framework SDKs can return true for certain combined authorization checks when the result should be false, allowing a gated action to proceed for a user who does not satisfy the full set of requested conditions. This call shape can be bypassed if certain conditions are met: a has() or auth.protect() call that combines a reverification check with any of role, permission, feature, or plan, or that combines a billing check (feature or plan) with a role or permission check. This vulnerability is fixed in @clerk/clerk-js 5.125.10 and 6.7.5.

Published 2026-05-11 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 8.1 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N.

EPSS exploit prediction

EPSS: 0.004 (35.2th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 35th percentile — 35.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.002 · newest: 0.004 · change: +0.002

Affected products

@Clerk Astro — versions >= 2.0.0, <= 2.17.10, >= 3.0.0, <= 3.0.17
@Clerk Backend — versions >= 2.0.0, <= 2.33.2, >= 3.0.0, <= 3.2.13
@Clerk Chrome-Extension — versions >= 1.3.5, <= 2.9.14, >= 3.0.0, <= 3.1.14
@Clerk Clerk-Expo — versions >= 2.2.11, <= 2.19.35
@Clerk Clerk-React — versions >= 5.9.0, <= 5.61.5
@Clerk Expo — versions >= 3.0.0, <= 3.2.1
@Clerk Express — versions >= 0.1.0, <= 1.7.78, >= 2.0.0, <= 2.1.5
@Clerk Fastify — versions >= 1.0.42, <= 2.6.30, >= 3.0.0, <= 3.1.15
@Clerk Hono — versions >= 0.0.2, <= 0.1.15
@Clerk Nextjs — versions >= 6.0.0, <= 6.39.2, >= 7.0.0, <= 7.2.3

Weakness classification (CWE)

References

github.com/clerk/javascript/security/advisories/GHSA-w24r-5266-9c3c (Mitigation, Vendor Advisory)

Frequently asked questions

What is CVE-2026-42349?: CVE-2026-42349 is a high-severity vulnerability in @Clerk Astro, classified under Improper Check for Unusual or Exceptional Conditions. CVSS score: 8.1/10. Published 2026-05-11.
How severe is CVE-2026-42349?: High severity. CVSS v3 base score is 8.1 out of 10.