{"id":"CVE-2026-66402","title":"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()","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 Commo…","severity":"critical","cvss":9.8,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","cwe":["CWE-295"],"vendor":"freerdp","product":"freerdp","affected":["freerdp < 3.29.0"],"patched":["freerdp 3.29.0"],"published":"2026-08-01","updated":"2026-10-02","sourceUpdated":"2026-10-02T19:08:13.673","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-66402","references":[{"url":"https://github.com/FreeRDP/FreeRDP/commit/b9533f07f98c25ed01c5f543b4d0ce73e120f5fd","label":"disclosure@vulncheck.com"},{"url":"https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-43hh-p3vw-hfx3","label":"disclosure@vulncheck.com"},{"url":"https://www.vulncheck.com/advisories/freerdp-before-tls-certificate-identity-validation-bypass","label":"disclosure@vulncheck.com"}],"tags":["nvd"],"epss":0.0034,"epssPercentile":0.27227,"ingestedAt":"2026-08-02T05:17:49.356Z","slug":"CVE-2026-66402","body":"## Overview\n\nFreeRDP 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.\n\n## Affected\n\n- `freerdp < 3.29.0`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `freerdp 3.29.0`","depth":"midnight","depthScore":54,"depthScoreParts":{"impact":53.9,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}