CVE-2026-35042
High · 7.5CVSS
7.5
EPSS
0.2%
Published
Apr 6, 2026
CISA due date
—
The record
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.
Affected packages
| Ecosystem | Package | Introduced | Fixed |
|---|---|---|---|
| npm | fast-jwt | 0 | No fix |
Related vulnerabilities
- GHSA-hm7r-c7qw-ghp6 fast-jwt accepts unknown `crit` header extensions (RFC 7515 violation) Same vulnerability
- CVE-2026-44351 fast-jwt provides fast JSON Web Token (JWT) implementation. Also affects fast-jwt
- GHSA-gmvf-9v4p-v8jc fast-jwt: JWT auth bypass due to empty HMAC secret accepted by async key resolver Also affects fast-jwt
- GHSA-cjw9-ghj4-fwxf fast-jwt has a ReDoS when using RegExp in allowed* leading to CPU exhaustion during token… Also affects fast-jwt
- GHSA-3j8v-cgw4-2g6q fast-jwt: Stateful RegExp (/g or /y) causes non-deterministic allowed-claim validation… Also affects fast-jwt
- CVE-2026-35040 fast-jwt provides fast JSON Web Token (JWT) implementation. Also affects fast-jwt
- CVE-2026-35041 fast-jwt provides fast JSON Web Token (JWT) implementation. Also affects fast-jwt
- CVE-2026-35039 fast-jwt provides fast JSON Web Token (JWT) implementation. Also affects fast-jwt