CVE-2026-109241 in FreeRDP
Summary
by MITRE • 10/12/2026
FreeRDP before 3.32.0 contains a NULL pointer dereference vulnerability in the client video redirection channel that allows malicious servers to crash clients by sending out-of-order messages. Attackers can send a Geometry CLEAR message that nulls presentation->geometry, then send VideoData that dereferences it, causing client denial of service.
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Analysis
by VulDB Data Team • 10/12/2026
The identified vulnerability resides within the FreeRDP software suite prior to version 3.32.0 and specifically affects the implementation of the remote desktop video redirection channel on the client side. This component is responsible for handling incoming video streams from a remote server, translating them into displayable frames for the local user interface. The core technical flaw stems from an improper validation of message ordering within this channel's state machine logic. Specifically, the vulnerability allows a malicious or compromised RDP server to exploit a race condition in how presentation geometry updates are processed relative to incoming video data packets. This scenario is classified under CWE-476, which denotes NULL Pointer Dereference, as the application fails to ensure that necessary structural pointers remain valid before attempting to access them during packet processing routines.
The exploitation mechanism relies on manipulating the sequence of messages sent by the server to disrupt the internal state consistency of the client's video rendering engine. An attacker can first transmit a Geometry CLEAR message, which instructs the client to reset or nullify its current presentation geometry data structures. In a correctly implemented system, subsequent operations that depend on this geometry would either be blocked until valid geometry is re-established or handled with appropriate error checking. However, due to the flaw in FreeRDP's logic, the application does not adequately guard against receiving VideoData packets immediately following such a clear operation without verifying that the underlying presentation object has been properly re-initialized. Consequently, when the client attempts to process the subsequent VideoData message, it references the now-nullified geometry pointer. This action triggers an immediate segmentation fault or access violation within the operating system's memory management subsystem, resulting in the abrupt termination of the FreeRDP application process.
From a security operations perspective, this vulnerability presents a significant risk for denial-of-service attacks against remote desktop infrastructure and end-user workstations relying on FreeRDP connections. Since the attack vector requires only network access to the RDP service and does not necessitate user interaction beyond establishing an initial connection, it is highly exploitable in environments where users connect to untrusted or potentially compromised servers. The impact is strictly limited to availability, as the crash prevents further use of the remote desktop session until the application is restarted by the administrator or end-user. This aligns with ATT&CK technique T1499, Endpoint Denial of Service, specifically under sub-techniques involving resource exhaustion through service disruption. While this vulnerability does not currently allow for arbitrary code execution or privilege escalation based on available information, it serves as a critical stability issue that can be leveraged to disrupt business continuity in remote access scenarios.
Mitigation strategies primarily involve upgrading the FreeRDP client software to version 3.32.0 or later, where this logic error has been corrected by implementing stricter state validation before processing video data streams. Organizations should also consider network-level controls such as firewalls and intrusion detection systems that monitor for anomalous RDP traffic patterns indicative of malformed message sequences. Additionally, deploying application whitelisting solutions can help prevent the execution of compromised or unpatched binaries if an exploit is attempted in a zero-day scenario before patches are applied. Regular patch management cycles should be enforced to ensure that all client endpoints utilizing FreeRDP remain updated with the latest security fixes provided by the maintainers.