{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "introduced": "0"
              },
              {
                "fixed": "6.3.1"
              }
            ],
            "source": "AFFECTED_FIELD"
          },
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "865c52262f39234a9b97524eb7f4821cf6d921ad"
            }
          ],
          "repo": "https://github.com/nearform/fast-jwt",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-8wpc-h4q6-8fxv"
  ],
  "database_specific": {
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
      "CWE-20",
      "CWE-347"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/107xxx/CVE-2026-107720.json"
  },
  "details": "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.",
  "id": "CVE-2026-107720",
  "modified": "2026-10-09T10:30:48.379547659Z",
  "published": "2026-10-08T21:44:06.843Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/107xxx/CVE-2026-107720.json"
    },
    {
      "type": "FIX",
      "url": "https://github.com/nearform/fast-jwt/commit/e22a151e83bf6d5e54e281216982d204d5665534"
    },
    {
      "type": "FIX",
      "url": "https://github.com/nearform/fast-jwt/pull/649"
    },
    {
      "type": "WEB",
      "url": "https://github.com/nearform/fast-jwt/releases/tag/v6.3.1"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/nearform/fast-jwt/security/advisories/GHSA-8wpc-h4q6-8fxv"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-107720"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "fast-jwt: createVerifier accepts unsigned JWTs when key is '' or null and algorithms is explicitly set"
}