CVE-2026-66402 PUBLISHED

FreeRDP before 3.29.0 TLS Certificate Identity Validation Bypass

Assigner: VulnCheck
Reserved: 26.07.2026 Published: 01.08.2026 Updated: 01.08.2026

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.

Metrics

CVSS 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
CVSS Score: 9.3

Product Status

Vendor FreeRDP
Product FreeRDP
Versions Default: unaffected
  • affected from 0 to 3.29.0 (excl.)
  • Version 3.29.0 is unaffected

Credits

  • 1121984919 reporter

References

Problem Types

  • Improper Certificate Validation CWE