CVE-2026-66402
Description
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.
Statement
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.
Mitigation
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.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.3 | N/A | 9.8 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | Low | N/A | High |
| Integrity Impact | None | N/A | High |
| Availability Impact | None | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Understanding the Weakness (CWE)
Non-Repudiation
Technical Impact: Hide Activities
The source of an attack will be difficult or impossible to determine. This can allow attacks to the system to continue without notice.
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