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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.","state":"PUBLISHED","assigner":"VulnCheck","published_at":"2026-08-01 13:16:57","updated_at":"2026-08-01 13:16:57"},"problem_types":["CWE-295","CWE-295 Improper Certificate 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before 3.29.0 TLS Certificate Identity Validation Bypass","CVE":"CVE-2026-66402","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"66402","Ordinal":"1","NoteData":"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.","Type":"Description","Title":"FreeRDP before 3.29.0 TLS Certificate Identity Validation Bypass"}]}}}