CVE-2026-121396
Description
A flaw was found in FreeRDP. A remote attacker operating a malicious Remote Desktop (RD) Gateway can cause a denial of service (DoS) by sending a crafted Request to Send (RTS) packet with malformed authentication padding. When parsed, this invalid padding triggers an internal assertion failure that abruptly terminates the connecting client process. This flaw only affects FreeRDP clients built with the WITH_VERBOSE_WINPR_ASSERT flag enabled.
Statement
Red Hat Enterprise Linux ships FreeRDP with WITH_VERBOSE_WINPR_ASSERT disabled (not set in RHEL 9, explicitly set to OFF in RHEL 10), so the vulnerable assertion is a no-op in production packages. RHEL systems are not affected by this vulnerability.
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 | 4.3 | N/A | 4.3 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | Required | N/A | Required |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | None | N/A | None |
| Availability Impact | Low | N/A | Low |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Crash, Exit, or Restart
While assertion is good for catching logic errors and reducing the chances of reaching more serious vulnerability conditions, an attacker can still cause a denial of service if they can trigger an assert statement, and if the scope of the assert() extends beyond the attacker's own session. For example, if a server handles multiple simultaneous connections, if an assert() occurs in one single connection that causes all other connections to be dropped, this could be a significant denial of service.
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