{"cve":"CVE-2026-107720","nvd":{"published":"2026-10-08T22:17:28.090","modified":"2026-10-09T15:17:08.947","status":"Deferred","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.","cvss_v4":null,"cvss_v3":{"version":"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},"cwes":["CWE-20","CWE-347"],"references":["https://github.com/nearform/fast-jwt/commit/e22a151e83bf6d5e54e281216982d204d5665534","https://github.com/nearform/fast-jwt/pull/649","https://github.com/nearform/fast-jwt/releases/tag/v6.3.1","https://github.com/nearform/fast-jwt/security/advisories/GHSA-8wpc-h4q6-8fxv","https://github.com/nearform/fast-jwt/security/advisories/GHSA-8wpc-h4q6-8fxv"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:58:01.639778232+00:00"},"epss":{"cve":"CVE-2026-107720","score":0.00324,"percentile":0.25195,"date":"2026-10-25"},"kev":null,"osv":[{"id":"GHSA-8wpc-h4q6-8fxv","url":"https://osv.dev/vulnerability/GHSA-8wpc-h4q6-8fxv","summary":"fast-jwt: createVerifier accepts unsigned JWTs when key is '' or null and algorithms is explicitly set","modified":"2026-10-08T22:15:07.105532249Z","packages":[{"ecosystem":"npm","name":"fast-jwt","purl":"pkg:npm/fast-jwt","ranges":["<6.3.1"],"fixed":["6.3.1"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}