CVE-2026-34950 fast-jwt has an incomplete fix for CVE-2023-48223: JWT Algorithm Confusion via Whitespace-Prefixed RSA Public Key

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 patch...

CVE-2026-34950

CVE-2026-34950 affects the fast-jwt library (6.1.0 and earlier). The publicKeyPemMatcher in fast-jwt/src/crypto.js uses an anchored regex starting with ^, which is defeated by any leading whitespace in the key string. This misclassifies RSA public keys with leading whitespace, allowing an attacke...

CVE-2026-34950 fast-jwt has an incomplete fix for CVE-2023-48223: JWT Algorithm Confusion via Whitespace-Prefixed RSA Public Key

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 patch...

GHSA-MVF2-F6GM-W987 fast-jwt: Incomplete fix for CVE-2023-48223: JWT Algorithm Confusion via Whitespace-Prefixed RSA Public Key

Summary The fix for GHSA-c2ff-88x2-x9pg CVE-2023-48223 is incomplete. 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 the CVE patched. Details The f...

CVE-2023-48223

fast-jwt prior to v3.3.2 contains a publicKeyPemMatcher bug that fails to cover all PEM formats for public keys, enabling an algorithm-confusion attack (HS256 signed with an RSA public key) when RS256 is used and the verifier does not explicitly specify an algorithm. A patch in v3.3.2 fixes this ...