{"id":"CVE-2026-45363","aliases":["GHSA-c32j-vqhx-rx3x"],"url":"https://o3.security/vulnerability/CVE-2026-45363","summary":"`jwt` (Ruby gem) - empty-key HMAC bypass","details":"ruby-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.","published":"2026-07-14T21:32:26.676Z","modified":"2026-08-12T03:51:43.507276555Z","cvss":{"score":9.1,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N"},"epss":{"score":0.00242,"percentile":0.15478,"asOf":"2026-08-14"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"RubyGems","name":"jwt","fixedVersion":"3.2.0"},{"ecosystem":"RubyGems","name":"jwt","fixedVersion":"2.10.3"}],"fix":{"url":"https://github.com/jwt/ruby-jwt/commit/9820020869ad147b941e49d96ab8beba35532964","label":"jwt/ruby-jwt@9820020"},"references":[{"type":"WEB","url":"https://github.com/jwt/ruby-jwt/releases/tag/v2.10.3"},{"type":"WEB","url":"https://github.com/jwt/ruby-jwt/releases/tag/v3.2.0"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/45xxx/CVE-2026-45363.json"},{"type":"ADVISORY","url":"https://github.com/jwt/ruby-jwt/security/advisories/GHSA-c32j-vqhx-rx3x"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-45363"},{"type":"FIX","url":"https://github.com/jwt/ruby-jwt/commit/9820020869ad147b941e49d96ab8beba35532964"},{"type":"FIX","url":"https://github.com/jwt/ruby-jwt/commit/db560b769a07bd9724e77ff505011ac01872106f"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:43.507276555Z"}}