CVE-2026-41248
Published: 24 April 2026
Summary
CVE-2026-41248 is a critical-severity Interpretation Conflict (CWE-436) vulnerability. Its CVSS base score is 9.1 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 24.1th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 AC-3 (Access Enforcement) and SI-2 (Flaw Remediation).
Deeper analysis
CVE-2026-41248 affects the createRouteMatcher function in the @clerk/nextjs, @clerk/nuxt, and @clerk/astro packages from Clerk JavaScript, the official JavaScript repository for Clerk authentication. Certain crafted requests can bypass middleware gating, allowing access to downstream handlers. Published on 2026-04-24, the vulnerability carries a CVSS score of 9.1 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N) and maps to CWEs 436 and 863.
Remote unauthenticated attackers can exploit this over the network with low attack complexity and no user interaction. By crafting specific requests, they bypass middleware protections to reach protected handlers, enabling high-impact violations of confidentiality and integrity, such as unauthorized access to sensitive data or functionality.
The issue is addressed in @clerk/astro versions 1.5.7, 2.17.10, and 3.0.15; @clerk/nextjs versions 5.7.6, 6.39.2, and 7.2.1; @clerk/nuxt versions 1.13.28 and 2.2.2; and @clerk/shared versions 2.22.1, 3.47.4, and 4.8.1. Additional details are available in the GitHub security advisory at https://github.com/clerk/javascript/security/advisories/GHSA-vqx2-fgx2-5wq9.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-25632
Vulnerability details
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,…
more
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
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
The vulnerability enables remote unauthenticated attackers to craft requests bypassing authentication middleware in public-facing web applications using Clerk packages, directly facilitating exploitation of public-facing applications for unauthorized access to sensitive data and functionality.
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Requires timely remediation of the specific flaw in createRouteMatcher across vulnerable Clerk packages to eliminate the middleware bypass vulnerability.
Mandates enforcement of approved access authorizations by middleware to block crafted requests from skipping gating and reaching protected downstream handlers.
Validates crafted request inputs to prevent bypass of route matching logic in Clerk authentication middleware.