FreeRDP before 3.29.0 TLS Certificate Identity Validation Bypass

{
  "id": "8ef71d2c3199dfc5ab4c88ad1b7bc40dd3f13be6c778a3f9a6fb4a00345cbabc",
  "url": "https://osv.dev/vulnerability/CVE-2026-66402",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "FreeRDP before 3.29.0 TLS Certificate Identity Validation Bypass",
    "summary": "FreeRDP before 3.29.0 (affected versions <= 3.28.0) contains multiple TLS certificate identity validation weaknesses in tls_verify_certificate(), tls_match_hostname(), and x509_utils_get_dns_names(). Because FreeRDP performs custom Common Name and DNS SAN string matching instead of using OpenSSL's length-aware identity validation APIs, it (1) truncates DNS SAN values at embedded NUL bytes (accepting e.g. 'victim.example\\0.attacker.example' as 'victim.example'), (2) accepts a matching Common Name even when non-matching DNS SAN entries are present, and (3) accepts IP-literal targets via DNS/CN matching without comparing iPAddress SANs. Under a trusted or misissued certificate chain, an attacker positioned to present such a certificate can bypass server identity verification, weakening TLS server authentication.",
    "evidence": "osv:CVE-2026-66402",
    "products": [],
    "severity": "critical",
    "structured": {
      "id": "CVE-2026-66402",
      "aliases": [
        "CVE-2026-66402",
        "GHSA-43hh-p3vw-hfx3"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/freerdp/freerdp",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "743f437f434c6814d3ba265c75cab14673bc2911"
                },
                {
                  "fixed": "b9533f07f98c25ed01c5f543b4d0ce73e120f5fd"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:freerdp:freerdp:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "3.29.0"
                      }
                    ],
                    "source": "CPE_RANGE"
                  },
                  {
                    "range": [
                      {
                        "fixed": "b9533f07f98c25ed01c5f543b4d0ce73e120f5fd"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "versions": [
            "3.5.1",
            "3.5.0",
            "3.4.0",
            "3.3.0",
            "3.2.0",
            "3.1.0",
            "3.0.0",
            "3.0.0-rc0",
            "3.0.0-beta4",
            "3.0.0-beta3",
            "3.0.0-beta2",
            "3.0.0-beta1",
            "2.0.0",
            "2.0.0-rc4",
            "2.0.0-rc3",
            "2.0.0-rc2",
            "2.0.0-rc1",
            "2.0.0-rc0",
            "2.0.0-beta1+android11",
            "2.0.0-beta1+android10",
            "1.2.0-beta1+android9",
            "1.2.0-beta1+android7",
            "1.1.0-beta+2013071101",
            "1.1.0-beta1+ios4",
            "1.1.0-beta1+android5",
            "1.1.0-beta1+android4",
            "1.1.0-beta1+ios3",
            "1.1.0-beta1+ios2",
            "1.1.0-beta1+android3",
            "1.1.0-beta1+android2",
            "1.1.0-beta1+ios1",
            "1.1.0-beta1",
            "1.0.1",
            "1.0.0",
            "1.0-beta5",
            "1.0-beta4",
            "1.0-beta2",
            "1.0-beta1"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-66402.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:45.832079255Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/66xxx/CVE-2026-66402.json",
        "https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-43hh-p3vw-hfx3",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-66402",
        "https://www.vulncheck.com/advisories/freerdp-before-tls-certificate-identity-validation-bypass",
        "https://github.com/FreeRDP/FreeRDP/commit/b9533f07f98c25ed01c5f543b4d0ce73e120f5fd"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-295"
        ],
        "cna_assigner": "VulnCheck",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/66xxx/CVE-2026-66402.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-66402",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 513619,
  "published_at": "2026-08-01T12:22:17.331+00:00"
}