{"id":"CVE-2026-107720","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-107720","generatedAt":"2026-10-28T03:39:39.023Z","title":"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.","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.","published":"2026-10-08T22:17:28.000Z","lastModified":"2026-10-09T15:17:09.000Z","status":"Deferred","sourceIdentifier":"security-advisories@github.com","cvss":{"version":"3.1","score":7.4,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N"},"cwe":["CWE-20","CWE-347"],"affected":[],"epss":{"score":0.00324,"percentile":0.25278,"date":"2026-10-27","history":[{"date":"2026-10-09","score":0.00256,"percentile":0.15848}]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (0.32%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[{"kind":"new","label":"New CVE","at":"2026-10-08T22:17:28.000Z","detail":{"score":"7.4","severity":"HIGH","publishedAt":"2026-10-08T22:17:28.090Z"},"summary":"New CVE, high severity (CVSS 7.4)."}],"references":[{"url":"https://github.com/nearform/fast-jwt/commit/e22a151e83bf6d5e54e281216982d204d5665534","source":"security-advisories@github.com"},{"url":"https://github.com/nearform/fast-jwt/pull/649","source":"security-advisories@github.com"},{"url":"https://github.com/nearform/fast-jwt/releases/tag/v6.3.1","source":"security-advisories@github.com"},{"url":"https://github.com/nearform/fast-jwt/security/advisories/GHSA-8wpc-h4q6-8fxv","source":"security-advisories@github.com"},{"url":"https://github.com/nearform/fast-jwt/security/advisories/GHSA-8wpc-h4q6-8fxv","source":"134c704f-9b21-4f2e-91b3-4a467353bcc0"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-107720","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}