{"id":"CVE-2026-107724","sourceIdentifier":"security-advisories@github.com","published":"2026-10-08T22:17:28.800","lastModified":"2026-10-09T16:17:23.740","vulnStatus":"Deferred","cveTags":[],"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":[{"source":"security-advisories@github.com","affectedData":[{"vendor":"nearform","product":"fast-jwt","versions":[{"version":">= 6.2.4, < 6.3.0","status":"affected"}]}]}],"metrics":{"cvssMetricV31":[{"source":"security-advisories@github.com","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N","baseScore":7.4,"baseSeverity":"HIGH","attackVector":"NETWORK","attackComplexity":"HIGH","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"NONE"},"exploitabilityScore":2.2,"impactScore":5.2}],"ssvcV203":[{"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","ssvcData":{"timestamp":"2026-10-09T15:51:21.495223Z","id":"CVE-2026-107724","options":[{"exploitation":"poc"},{"automatable":"no"},{"technicalImpact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}]},"weaknesses":[{"source":"security-advisories@github.com","type":"Secondary","description":[{"lang":"en","value":"CWE-347"}]}],"references":[{"url":"https://github.com/nearform/fast-jwt/commit/10f9591349199ed2ab9fa1748ce92cdca697f6cf","source":"security-advisories@github.com"},{"url":"https://github.com/nearform/fast-jwt/pull/636","source":"security-advisories@github.com"},{"url":"https://github.com/nearform/fast-jwt/releases/tag/v6.3.0","source":"security-advisories@github.com"},{"url":"https://github.com/nearform/fast-jwt/security/advisories/GHSA-g3jj-5cmm-3hxx","source":"security-advisories@github.com"},{"url":"https://github.com/nearform/fast-jwt/security/advisories/GHSA-g3jj-5cmm-3hxx","source":"134c704f-9b21-4f2e-91b3-4a467353bcc0"}]}