{"id":"CVE-2026-66402","summary":"FreeRDP before 3.29.0 TLS Certificate Identity Validation Bypass","details":"FreeRDP before 3.29.0 (affected versions \u003c= 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.","aliases":["GHSA-43hh-p3vw-hfx3"],"modified":"2026-08-04T11:51:18.569643507Z","published":"2026-08-01T12:22:17.331Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/66xxx/CVE-2026-66402.json","cna_assigner":"VulnCheck","cwe_ids":["CWE-295"]},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/66xxx/CVE-2026-66402.json"},{"type":"ADVISORY","url":"https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-43hh-p3vw-hfx3"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-66402"},{"type":"ADVISORY","url":"https://www.vulncheck.com/advisories/freerdp-before-tls-certificate-identity-validation-bypass"},{"type":"FIX","url":"https://github.com/FreeRDP/FreeRDP/commit/b9533f07f98c25ed01c5f543b4d0ce73e120f5fd"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/freerdp/freerdp","events":[{"introduced":"0"},{"fixed":"743f437f434c6814d3ba265c75cab14673bc2911"}],"database_specific":{"source":"AFFECTED_FIELD","extracted_events":[{"introduced":"0"},{"fixed":"3.29.0"}]}}],"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"}}],"schema_version":"1.8.0","severity":[{"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"}]}