{"cve":"CVE-2026-44351","nvd":{"published":"2026-05-13T20:16:22.860","modified":"2026-10-26T14:10:00.130","status":"Deferred","description":"fast-jwt provides fast JSON Web Token (JWT) implementation. Prior to 6.2.4, a critical authentication-bypass vulnerability in fast-jwt's async key-resolver flow allows any unauthenticated attacker to forge arbitrary JWTs that are accepted as authentic. When the application's key resolver returns an empty string (''), for example via the common keys[decoded.header.kid] || '' JWKS-style fallback, fast-jwt converts it to a zero-length Buffer, hands it to crypto.createSecretKey, derives allowedAlgorithms = ['HS256','HS384','HS512'] from it, and then verifies the token's signature against an empty-key HMAC. The attacker simply computes HMAC-SHA256(key='', input='${header}.${payload}'), which Node accepts without complaint — and the verifier returns the attacker-chosen payload (sub, admin, scopes, etc.) as authentic. This vulnerability is fixed in 6.2.4.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","score":9.1},"cwes":["CWE-287","CWE-326","CWE-1391"],"references":["https://github.com/nearform/fast-jwt/security/advisories/GHSA-gmvf-9v4p-v8jc","https://github.com/nearform/fast-jwt/security/advisories/GHSA-gmvf-9v4p-v8jc"],"products":[],"source":"nvd","synced_at":"2026-10-26T14:27:29.784594657+00:00"},"epss":{"cve":"CVE-2026-44351","score":0.0025,"percentile":0.16244,"date":"2026-10-26"},"kev":null,"osv":[{"id":"GHSA-gmvf-9v4p-v8jc","url":"https://osv.dev/vulnerability/GHSA-gmvf-9v4p-v8jc","summary":"fast-jwt: JWT auth bypass due to empty HMAC secret accepted by async key resolver","modified":"2026-05-14T20:49:42.175667Z","packages":[{"ecosystem":"npm","name":"fast-jwt","purl":"pkg:npm/fast-jwt","ranges":["<6.2.4"],"fixed":["6.2.4"]}]}],"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."]}