CVE-2026-66402

A flaw was found in FreeRDP. This flaw involves multiple weaknesses in how FreeRDP validates TLS (Transport Layer Security) certificates. FreeRDP's custom validation logic can incorrectly process DNS Subject Alternative Name (SAN) values, accept Common Names without proper comparison to other SAN entries, and fail to validate IP address SANs for IP-literal targets. An attacker, by presenting a specially crafted certificate, could exploit these weaknesses to bypass server identity verification, potentially allowing them to impersonate a legitimate server and compromise the security of the connection.

This issue is classified as Moderate severity because successful exploitation requires an attacker to be in a man-in-the-middle network position using a specially crafted certificate, allowing them to bypass server identity verification and impersonate a target server without directly enabling code execution or host system compromise.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.