{"id":"CVE-2026-66402","state":"PUBLISHED","title":"FreeRDP before 3.29.0 TLS Certificate Identity Validation Bypass","description":"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.","publishedAt":"2026-08-01T12:22:17.331Z","updatedAt":"2026-08-05T03:56:18.042Z","severity":{"score":9.3,"label":"Critical","version":"4.0","vector":"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","source":"VulnCheck"},"assigner":"VulnCheck","products":["FreeRDP FreeRDP"],"affected":[{"vendor":"FreeRDP","product":"FreeRDP","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThan":"3.29.0","versionType":"semver"},{"version":"3.29.0","status":"unaffected","versionType":"semver"}]}],"references":["https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-43hh-p3vw-hfx3","https://github.com/FreeRDP/FreeRDP/commit/b9533f07f98c25ed01c5f543b4d0ce73e120f5fd","https://www.vulncheck.com/advisories/freerdp-before-tls-certificate-identity-validation-bypass"],"weaknesses":["CWE-295"],"ingestedAt":"2026-10-29T20:12:41.951Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/66xxx/CVE-2026-66402.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-66402","state":"PUBLISHED","datePublished":"2026-08-01T12:22:17.331Z","dateUpdated":"2026-08-05T03:56:18.042Z","assignerShortName":"VulnCheck","assignerOrgId":"83251b91-4cc7-4094-a5c7-464a1b83ea10","dateReserved":"2026-07-26T12:22:34.139Z"},"containers":{"cna":{"title":"FreeRDP before 3.29.0 TLS Certificate Identity Validation Bypass","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"FreeRDP","product":"FreeRDP","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThan":"3.29.0","versionType":"semver"},{"version":"3.29.0","status":"unaffected","versionType":"semver"}]}],"references":[{"url":"https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-43hh-p3vw-hfx3","tags":["vendor-advisory"],"name":"GitHub Security Advisory (GHSA-43hh-p3vw-hfx3)"},{"url":"https://github.com/FreeRDP/FreeRDP/commit/b9533f07f98c25ed01c5f543b4d0ce73e120f5fd","tags":["patch"],"name":"Patch Commit"},{"url":"https://www.vulncheck.com/advisories/freerdp-before-tls-certificate-identity-validation-bypass","name":"VulnCheck Advisory: FreeRDP before 3.29.0 TLS Certificate Identity Validation Bypass","tags":["third-party-advisory"]}],"metrics":[{"cvssV4_0":{"Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","Safety":"NOT_DEFINED","attackComplexity":"LOW","attackRequirements":"NONE","attackVector":"NETWORK","baseScore":9.3,"baseSeverity":"CRITICAL","exploitMaturity":"NOT_DEFINED","privilegesRequired":"NONE","providerUrgency":"NOT_DEFINED","subAvailabilityImpact":"NONE","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","userInteraction":"NONE","valueDensity":"NOT_DEFINED","vectorString":"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","version":"4.0","vulnAvailabilityImpact":"HIGH","vulnConfidentialityImpact":"HIGH","vulnIntegrityImpact":"HIGH","vulnerabilityResponseEffort":"NOT_DEFINED"},"format":"CVSS"},{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"HIGH","baseScore":9.8,"baseSeverity":"CRITICAL","confidentialityImpact":"HIGH","integrityImpact":"HIGH","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","version":"3.1"},"format":"CVSS"}],"problemTypes":[{"descriptions":[{"cweId":"CWE-295","lang":"en","description":"Improper Certificate Validation","type":"CWE"}]}],"providerMetadata":{"shortName":"VulnCheck","orgId":"83251b91-4cc7-4094-a5c7-464a1b83ea10","dateUpdated":"2026-08-01T12:22:17.331Z"},"datePublic":"2026-07-15T00:00:00.000Z","cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:a:freerdp:freerdp:*:*:*:*:*:*:*:*","versionEndExcluding":"3.29.0"}]}]}],"credits":[{"lang":"en","value":"1121984919","type":"reporter"}],"x_generator":{"engine":"vulncheck-endgame"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-08-04T00:00:00+00:00","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"total"}],"role":"CISA Coordinator","version":"2.0.3","id":"CVE-2026-66402"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-08-05T03:56:18.042Z"}}]}}}