{"id":"CVE-2026-45363","state":"PUBLISHED","title":"`jwt` (Ruby gem) - empty-key HMAC bypass","description":"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.","publishedAt":"2026-07-14T21:32:26.676Z","updatedAt":"2026-09-19T18:07:54.033Z","severity":{"score":9.1,"label":"Critical","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","source":"GitHub_M"},"assigner":"GitHub_M","products":["jwt ruby-jwt"],"affected":[{"vendor":"jwt","product":"ruby-jwt","versions":[{"version":"< 2.10.3","status":"affected"},{"version":">= 3.0.0, < 3.2.0","status":"affected"}]}],"references":["https://github.com/jwt/ruby-jwt/security/advisories/GHSA-c32j-vqhx-rx3x","https://github.com/jwt/ruby-jwt/commit/9820020869ad147b941e49d96ab8beba35532964","https://github.com/jwt/ruby-jwt/commit/db560b769a07bd9724e77ff505011ac01872106f","https://github.com/jwt/ruby-jwt/releases/tag/v2.10.3","https://github.com/jwt/ruby-jwt/releases/tag/v3.2.0","https://lists.debian.org/debian-lts-announce/2026/09/msg00022.html"],"weaknesses":["CWE-287","CWE-326","CWE-1391"],"ingestedAt":"2026-10-29T20:12:07.131Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/45xxx/CVE-2026-45363.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-45363","state":"PUBLISHED","datePublished":"2026-07-14T21:32:26.676Z","dateUpdated":"2026-09-19T18:07:54.033Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-05-12T00:51:29.085Z"},"containers":{"cna":{"title":"`jwt` (Ruby gem) - empty-key HMAC bypass","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"jwt","product":"ruby-jwt","versions":[{"version":"< 2.10.3","status":"affected"},{"version":">= 3.0.0, < 3.2.0","status":"affected"}]}],"references":[{"url":"https://github.com/jwt/ruby-jwt/security/advisories/GHSA-c32j-vqhx-rx3x","name":"https://github.com/jwt/ruby-jwt/security/advisories/GHSA-c32j-vqhx-rx3x","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/jwt/ruby-jwt/commit/9820020869ad147b941e49d96ab8beba35532964","name":"https://github.com/jwt/ruby-jwt/commit/9820020869ad147b941e49d96ab8beba35532964","tags":["x_refsource_MISC"]},{"url":"https://github.com/jwt/ruby-jwt/commit/db560b769a07bd9724e77ff505011ac01872106f","name":"https://github.com/jwt/ruby-jwt/commit/db560b769a07bd9724e77ff505011ac01872106f","tags":["x_refsource_MISC"]},{"url":"https://github.com/jwt/ruby-jwt/releases/tag/v2.10.3","name":"https://github.com/jwt/ruby-jwt/releases/tag/v2.10.3","tags":["x_refsource_MISC"]},{"url":"https://github.com/jwt/ruby-jwt/releases/tag/v3.2.0","name":"https://github.com/jwt/ruby-jwt/releases/tag/v3.2.0","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":9.1,"baseSeverity":"CRITICAL","confidentialityImpact":"HIGH","integrityImpact":"HIGH","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-287","lang":"en","description":"CWE-287: Improper Authentication","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-326","lang":"en","description":"CWE-326: Inadequate Encryption Strength","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-1391","lang":"en","description":"CWE-1391: Use of Weak Credentials","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-07-14T21:34:05.174Z"},"source":{"advisory":"GHSA-c32j-vqhx-rx3x","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-07-15T13:24:12.081532Z","id":"CVE-2026-45363","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-07-15T13:26:21.205Z"}},{"title":"CVE Program Container","references":[{"url":"https://lists.debian.org/debian-lts-announce/2026/09/msg00022.html"}],"providerMetadata":{"shortName":"CVE","orgId":"af854a3a-2127-422b-91ae-364da2661108","dateUpdated":"2026-09-19T18:07:54.033Z"}}]}}}