Vulnerability Description
fast-jwt provides fast JSON Web Token (JWT) implementation. From 5.0.0 to 6.2.0, a denial-of-service condition exists in fast-jwt when the allowedAud verification option is configured using a regular expression. Because the aud claim is attacker-controlled and the library evaluates it against the supplied RegExp, a crafted JWT can trigger catastrophic backtracking in the JavaScript regex engine, resulting in significant CPU consumption during verification. This vulnerability is fixed in 6.2.1.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Nearform | Fast-Jwt | >= 5.0.0, < 6.2.1 |
Related Weaknesses (CWE)
References
- https://github.com/nearform/fast-jwt/commit/b0be0ca161593836a153d5180ca5358ad9b5Patch
- https://github.com/nearform/fast-jwt/pull/595Issue TrackingPatch
- https://github.com/nearform/fast-jwt/releases/tag/v6.2.1ProductRelease Notes
- https://github.com/nearform/fast-jwt/security/advisories/GHSA-cjw9-ghj4-fwxfExploitMitigationVendor Advisory
- https://github.com/nearform/fast-jwt/security/advisories/GHSA-cjw9-ghj4-fwxfExploitMitigationVendor Advisory
FAQ
What is CVE-2026-35041?
CVE-2026-35041 is a vulnerability with a CVSS score of 4.2 (MEDIUM). fast-jwt provides fast JSON Web Token (JWT) implementation. From 5.0.0 to 6.2.0, a denial-of-service condition exists in fast-jwt when the allowedAud verification option is configured using a regular ...
How severe is CVE-2026-35041?
CVE-2026-35041 has been rated MEDIUM with a CVSS base score of 4.2/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-35041?
Check the references section above for vendor advisories and patch information. Affected products include: Nearform Fast-Jwt.