Vulnerability Description
fast-jwt provides fast JSON Web Token (JWT) implementation. In 6.1.0 and earlier, fast-jwt does not validate the crit (Critical) Header Parameter defined in RFC 7515 §4.1.11. When a JWS token contains a crit array listing extensions that fast-jwt does not understand, the library accepts the token instead of rejecting it. This violates the MUST requirement in the RFC.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Nearform | Fast-Jwt | < 6.2.0 |
Related Weaknesses (CWE)
References
- https://github.com/nearform/fast-jwt/security/advisories/GHSA-hm7r-c7qw-ghp6ExploitMitigationVendor Advisory
- https://www.rfc-editor.org/rfc/rfc7515.html#section-4.1.11Technical Description
- https://github.com/nearform/fast-jwt/security/advisories/GHSA-hm7r-c7qw-ghp6ExploitMitigationVendor Advisory
FAQ
What is CVE-2026-35042?
CVE-2026-35042 is a vulnerability with a CVSS score of 7.5 (HIGH). fast-jwt provides fast JSON Web Token (JWT) implementation. In 6.1.0 and earlier, fast-jwt does not validate the crit (Critical) Header Parameter defined in RFC 7515 §4.1.11. When a JWS token contains...
How severe is CVE-2026-35042?
CVE-2026-35042 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-35042?
Check the references section above for vendor advisories and patch information. Affected products include: Nearform Fast-Jwt.