Improper Certificate Validation in FreeRDP - CVE-2026-66402
Published: July 16, 2026 / Updated: September 14, 2026
Vulnerability identifier: #VU137820
CSH Severity: Medium
CVSS v4: 6.3 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-66402
CWE-ID: CWE-295
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to bypass TLS server identity validation.
The vulnerability exists due to improper certificate validation in x509_utils_get_dns_names() when parsing DNS subject alternative name values containing embedded NUL bytes. A remote attacker can present a specially crafted certificate to bypass TLS server identity validation.
Exploitation requires a certificate chain trusted by the FreeRDP client.
Affected software
FreeRDP
How to mitigate CVE-2026-66402
Install security update from vendor's website.
FreeRDP - update to 3.29.0