Vulnerability Details CVE-2026-35042
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 ยง4.1.11. 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.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.0
EPSS Ranking 2.8%
CVSS Severity
CVSS v3 Score 7.5