CVE-2026-107724

CVE-2026-107724 · fast-jwt treats raw public JWK JSON as an HMAC secret, enabling HS256 token forgery

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fast-jwt provides fast JSON Web Token (JWT) implementation. In 6.2.4, fast-jwt can classify raw serialized public JWK or JWKS JSON as an HMAC secret because src/crypto.js performDetectPublicKeyAlgorithms treats non-PEM strings as symmetric key material. If HS256 is explicitly allowed or inferred, an attacker who knows the exact serialized public-key bytes can use those bytes as an HMAC key and create a token containing arbitrary claims that createVerifier accepts. Serialization ordering or whitespace differences can prevent exploitation, and applications using supported PEM keys with an asymmetric-only algorithm allowlist are not affected. This issue is fixed in version 6.3.0.

CVSS 7.4 · Élevée · EPSS 0,3% · Correctif disponible

Publication

2026-10-08T21:53:01.909Z

Mise à jour

2026-10-09T15:51:27.488Z

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