CVE-2026-34950
Critical · 9.1CVSS
9.1
EPSS
0.3%
Published
Apr 6, 2026
CISA due date
—
The record
fast-jwt provides fast JSON Web Token (JWT) implementation. In 6.1.0 and earlier, the publicKeyPemMatcher regex in fast-jwt/src/crypto.js uses a ^ anchor that is defeated by any leading whitespace in the key string, re-enabling the exact same JWT algorithm confusion attack that CVE-2023-48223 patched.
Affected packages
| Ecosystem | Package | Introduced | Fixed |
|---|---|---|---|
| npm | fast-jwt | 0 | 6.2.0 |
Related vulnerabilities
- GHSA-mvf2-f6gm-w987 fast-jwt: Incomplete fix for CVE-2023-48223: JWT Algorithm Confusion via… 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