p PatchFirst

CVE-2026-107724

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

This page contains facts from public vulnerability sources. Check the original advisory before updating.

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 · High · EPSS 0.3% · Fix available

Published
Updated

Stack: node

Affected products and versions

  • fast-jwt

    Versions
    • >= 6.2.4, < 6.3.0: Affected

    No fix published

  • fast-jwt npm

    Versions
    • 6.2.4
    Affected ranges
    • SEMVER: ≥ 6.2.4, < 6.3.0

    Update to 6.3.0

Original sources

Check your server →