{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "cpe": "cpe:2.3:a:wolfssl:wolfssl:*:*:*:*:*:*:*:*",
            "extracted_events": [
              {
                "introduced": "3.15.5"
              },
              {
                "last_affected": "5.9.1"
              },
              {
                "fixed": "5.9.2"
              }
            ],
            "source": [
              "AFFECTED_FIELD",
              "CPE_RANGE"
            ]
          },
          "events": [
            {
              "introduced": "11810160b47ad37968fea375bdc6ad26b9973cd5"
            },
            {
              "fixed": "ac01707f552c611fbd135cc723b2682b3e7f80f2"
            }
          ],
          "repo": "https://github.com/wolfssl/wolfssl",
          "type": "GIT"
        }
      ]
    }
  ],
  "database_specific": {
    "cna_assigner": "wolfSSL",
    "cwe_ids": [
      "CWE-347"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/6xxx/CVE-2026-6331.json"
  },
  "details": "HMAC zero-length tag forgery in EVP_DigestVerifyFinal, where a zero-length tag could be accepted as valid during HMAC verification. In the OpenSSL-compatibility HMAC verify path the supplied signature length was only checked as not exceeding the MAC length, so a zero-length or otherwise truncated tag could pass verification. The fix requires the supplied tag length to exactly equal the MAC length and rejects a zero-length MAC, so a forged short or empty tag is no longer accepted.",
  "id": "CVE-2026-6331",
  "modified": "2026-07-16T03:30:57.469317760Z",
  "published": "2026-06-25T20:56:25.876Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://www.wolfssl.com/docs/security-vulnerabilities/"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/6xxx/CVE-2026-6331.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-6331"
    },
    {
      "type": "FIX",
      "url": "https://github.com/wolfSSL/wolfssl/pull/10192"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/wolfSSL/wolfssl"
    }
  ],
  "schema_version": "1.8.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:L/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "HMAC zero-length tag forgery in EVP_DigestVerifyFinal"
}