{"id":"CVE-2026-107720","revision":"310b78fdf331467cb68ca2da91fdf4fc","records":[{"revision":"310b78fdf331467cb68ca2da91fdf4fc","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-107720","aliases":[],"title":"fast-jwt: createVerifier accepts unsigned JWTs when key is '' or null and algorithms is explicitly set","description":"fast-jwt provides fast JSON Web Token (JWT) implementation. Prior to 6.3.1, fast-jwt createVerifier accepts an unsigned JWT when key is an empty string or null and algorithms is a non-empty allowlist. Falsy synchronous keys bypass prepareKeyOrSecret, allowedAlgorithms remains active, hasKey is false, and the empty signature avoids the verifySignature gate. An attacker can therefore submit a token containing arbitrary claims without possessing a signing key, resulting in authentication or authorization bypass. Claim validators still run, and non-empty keys, an empty key without algorithms, and the async key resolver path do not have this behavior. This issue is fixed in version 6.3.1.","state":0,"publishedAt":"2026-10-08T21:44:06.843+00:00","modifiedAt":"2026-10-09T14:32:14.931+00:00","affected":[{"ecosystem":"Vendor product","name":"fast-jwt","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"vendor\": \"nearform\",\n                    \"product\": \"fast-jwt\",\n                    \"versions\": [\n                        {\n                            \"version\": \"< 6.3.1\",\n                            \"status\": \"affected\"\n                        }\n                    ]\n                }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N","score":7.4,"severity":"HIGH"}],"references":["https://github.com/nearform/fast-jwt/security/advisories/GHSA-8wpc-h4q6-8fxv","https://github.com/nearform/fast-jwt/pull/649","https://github.com/nearform/fast-jwt/commit/e22a151e83bf6d5e54e281216982d204d5665534","https://github.com/nearform/fast-jwt/releases/tag/v6.3.1"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-107720","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-107720","identifiers":["CVE-2026-107720"]},"retained":false,"historicalAffected":[]}],"coverage":[]}