CVE-2026-35042 fast-jwt accepts unknown `crit` header extensions (RFC 7515 §4.1.11 MUST violation)

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...

EUVD-2026-11728

PyJWT accepts unknown crit header extensions...