CVE-2026-41248

Critical

Published: 24 April 2026

Published

24 April 2026

Modified

29 April 2026

KEV Added

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Patch

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

EPSS Score 0.0011 29.1th percentile

Risk Priority 18 60% EPSS · 20% KEV · 20% CVSS

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 29.1th 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).

Threat & Defense at a Glance

What attackers do: exploitation maps to Exploit Public-Facing Application (T1190). What defenders deploy: see the NIST 800-53 controls recommended below.

Threat & Defense Details

Mitigating Controls (NIST 800-53 r5)AI

SI-2 Flaw Remediation good match

prevent

Requires timely remediation of the specific flaw in createRouteMatcher across vulnerable Clerk packages to eliminate the middleware bypass vulnerability.

AC-3 Access Enforcement good match

prevent

Mandates enforcement of approved access authorizations by middleware to block crafted requests from skipping gating and reaching protected downstream handlers.

SI-10 Information Input Validation partial match

prevent

Validates crafted request inputs to prevent bypass of route matching logic in Clerk authentication middleware.

MITRE ATT&CK Enterprise TechniquesAI

T1190 Exploit Public-Facing Application Initial Access

Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.

attack.mitre.org →

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.

Confidence: HIGH · MITRE ATT&CK Enterprise v19.0

NVD Description

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

Deeper analysisAI

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.