CVE-2026-121958
Description
A flaw was found in FreeRDP. This vulnerability allows a remote attacker to cause a Denial of Service (DoS) or potentially execute arbitrary code on the client system. An attacker operating a malicious Remote Desktop Protocol (RDP) server, or acting in a man-in-the-middle position, can exploit this issue by sending specially crafted graphics pipeline commands. This occurs due to improper surface key truncation, causing an internal table to become inconsistent and triggering a heap-based buffer overflow when data is written past allocated memory boundaries.
Statement
This vulnerability is rated as Important severity because an untrusted or compromised remote desktop server can trigger heap memory corruption in the client process, potentially leading to arbitrary code execution or application crash. To exploit this flaw, a user must actively establish a remote desktop connection to a rogue server or have their traffic intercepted by a malicious intermediary. Red Hat Enterprise Linux systems acting purely as remote desktop servers or that do not initiate outbound connections to untrusted endpoints are not exposed to this issue.
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.
--- CME Mitigation Guidance (2026-11-06) ---
Disclaimer: The following mitigation solutions are provided as a courtesy, pending the application of an official patch. This content was generated utilizing AI tools in conjunction with data from https://cmetaxonomy.org. Customers are advised to independently evaluate and test these temporary mitigations within their own infrastructure.
The highest-value action is to disable the RDPGFX dynamic virtual channel or restrict FreeRDP client sessions from connecting to untrusted RDP endpoints: upgrade to the fixed Freerdp builds, which apply the documented input check, closing all 3 injection vectors (malicious RDP server connection, man-in-the-middle RDP traffic interception, crafted RDPGFX pipeline commands). Until patched, this is a concern on FreeRDP clients initiating connections to untrusted RDP servers or over untrusted networks with RDPGFX enabled, so Restrict FreeRDP client connections to verified RDP endpoints, enforce network encryption against interception, and disable the RDPGFX dynamic virtual channel in client configurations. As a compensating measure, Randomize process memory layouts with ASLR to impede reliable arbitrary code execution, Enforce full RELRO and PIE to protect the Global Offset Table from overwrites during heap corruption exploitation, Enable Control Flow Integrity to validate indirect call targets and block control-flow hijacking, Deploy EDR agents to detect anomalous post-exploitation behaviors and child processes spawned by FreeRDP, and Enforce non-executable memory protections using the NX/XD bit to block execution of shellcode in heap pages. These controls limit blast radius and contain exploitation, but they do not fix the underlying surface key truncation defect — apply the upstream patch to fully remediate.
Highest-impact CME: CME-101 ASLR (Address Space Layout Randomization) (medium)
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 | 8.8 | N/A | 8.8 |
| 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 | High | N/A | High |
| Integrity Impact | High | N/A | High |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Understanding the Weakness (CWE)
Integrity
Technical Impact: Modify Memory; Execute Unauthorized Code or Commands
Write operations could cause memory corruption. In some cases, an adversary can modify control data such as return addresses in order to execute unexpected code.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
Attempting to access out-of-range, invalid, or unauthorized memory could cause the product to crash.
Other
Technical Impact: Unexpected State
Subsequent write operations can produce undefined or unexpected results.
Frequently Asked Questions
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