{"id":"CVE-2026-107724","published":"2026-10-08T22:17:28.800","lastModified":"2026-10-09T16:17:23.740","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.","cvssScore":7.4,"cvssSeverity":"HIGH","cvssVector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N","cwes":["CWE-347"],"vendors":[],"products":[],"references":[{"url":"https://github.com/nearform/fast-jwt/commit/10f9591349199ed2ab9fa1748ce92cdca697f6cf","tags":[]},{"url":"https://github.com/nearform/fast-jwt/pull/636","tags":[]},{"url":"https://github.com/nearform/fast-jwt/releases/tag/v6.3.0","tags":[]},{"url":"https://github.com/nearform/fast-jwt/security/advisories/GHSA-g3jj-5cmm-3hxx","tags":[]},{"url":"https://github.com/nearform/fast-jwt/security/advisories/GHSA-g3jj-5cmm-3hxx","tags":[]}],"exploitRefs":[{"url":"https://github.com/nearform/fast-jwt/commit/10f9591349199ed2ab9fa1748ce92cdca697f6cf","tags":[]},{"url":"https://github.com/nearform/fast-jwt/pull/636","tags":[]},{"url":"https://github.com/nearform/fast-jwt/releases/tag/v6.3.0","tags":[]},{"url":"https://github.com/nearform/fast-jwt/security/advisories/GHSA-g3jj-5cmm-3hxx","tags":[]},{"url":"https://github.com/nearform/fast-jwt/security/advisories/GHSA-g3jj-5cmm-3hxx","tags":[]}],"hasPoc":true,"ai":null}