{"id":"CVE-2026-107724","state":"PUBLISHED","title":"fast-jwt treats raw public JWK JSON as an HMAC secret, enabling HS256 token forgery","description":"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.","publishedAt":"2026-10-08T21:53:01.909Z","updatedAt":"2026-10-09T15:51:27.488Z","severity":{"score":7.4,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N","source":"GitHub_M"},"assigner":"GitHub_M","products":["nearform fast-jwt"],"affected":[{"vendor":"nearform","product":"fast-jwt","versions":[{"version":">= 6.2.4, < 6.3.0","status":"affected"}]}],"references":["https://github.com/nearform/fast-jwt/security/advisories/GHSA-g3jj-5cmm-3hxx","https://github.com/nearform/fast-jwt/pull/636","https://github.com/nearform/fast-jwt/commit/10f9591349199ed2ab9fa1748ce92cdca697f6cf","https://github.com/nearform/fast-jwt/releases/tag/v6.3.0"],"weaknesses":["CWE-347"],"ingestedAt":"2026-10-29T20:10:23.711Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/107xxx/CVE-2026-107724.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-107724","state":"PUBLISHED","datePublished":"2026-10-08T21:53:01.909Z","dateUpdated":"2026-10-09T15:51:27.488Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-10-08T17:21:52.976Z"},"containers":{"cna":{"title":"fast-jwt treats raw public JWK JSON as an HMAC secret, enabling HS256 token forgery","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"nearform","product":"fast-jwt","versions":[{"version":">= 6.2.4, < 6.3.0","status":"affected"}]}],"references":[{"url":"https://github.com/nearform/fast-jwt/security/advisories/GHSA-g3jj-5cmm-3hxx","name":"https://github.com/nearform/fast-jwt/security/advisories/GHSA-g3jj-5cmm-3hxx","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/nearform/fast-jwt/pull/636","name":"https://github.com/nearform/fast-jwt/pull/636","tags":["x_refsource_MISC"]},{"url":"https://github.com/nearform/fast-jwt/commit/10f9591349199ed2ab9fa1748ce92cdca697f6cf","name":"https://github.com/nearform/fast-jwt/commit/10f9591349199ed2ab9fa1748ce92cdca697f6cf","tags":["x_refsource_MISC"]},{"url":"https://github.com/nearform/fast-jwt/releases/tag/v6.3.0","name":"https://github.com/nearform/fast-jwt/releases/tag/v6.3.0","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"HIGH","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":7.4,"baseSeverity":"HIGH","confidentialityImpact":"HIGH","integrityImpact":"HIGH","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-347","lang":"en","description":"CWE-347: Improper Verification of Cryptographic Signature","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-10-08T21:53:01.909Z"},"source":{"advisory":"GHSA-g3jj-5cmm-3hxx","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","references":[{"url":"https://github.com/nearform/fast-jwt/security/advisories/GHSA-g3jj-5cmm-3hxx","tags":["exploit"]}],"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-10-09T15:51:21.495223Z","id":"CVE-2026-107724","options":[{"Exploitation":"poc"},{"Automatable":"no"},{"Technical Impact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-09T15:51:27.488Z"}}]}}}