23 Oct 2026 15:48:27 UTC
`jwt` (Ruby gem) - empty-key HMAC bypass
cve-program · CVE-2026-45363 · Published
CVE-2026-45363
`jwt` (Ruby gem) - empty-key HMAC bypass
CVSS 3.1 9.1 CRITICALCheck source for fixed versionsKEV status unknown
cve-program · CVE-2026-45363
Publishedruby-jwt is a Ruby implementation of the RFC 7519 OAuth JSON Web Token standard. Prior to 2.10.3 and 3.2.0, JWT.decode(token, '', true, algorithm: 'HS256') accepts an attacker-forged token because OpenSSL::HMAC.digest('SHA256', '', payload) returns a valid digest under an empty key and no empty-key precondition exists in the HMAC algorithm. The same path is reached when a keyfinder block or key_finder: argument returns an empty string, nil, or an array containing nil for an unknown key, affecting HS256, HS384, and HS512 verification through JWT.decode and JWT::EncodedToken#verify_signature!. This issue is fixed in versions 2.10.3 and 3.2.0.
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