CVE-2023-39351 in FreeRDP
Summary
by MITRE • 08/31/2023
FreeRDP is a free implementation of the Remote Desktop Protocol (RDP), released under the Apache license. Affected versions of FreeRDP are subject to a Null Pointer Dereference leading a crash in the RemoteFX (rfx) handling. Inside the `rfx_process_message_tileset` function, the program allocates tiles using `rfx_allocate_tiles` for the number of numTiles. If the initialization process of tiles is not completed for various reasons, tiles will have a NULL pointer. Which may be accessed in further processing and would cause a program crash. This issue has been addressed in versions 2.11.0 and 3.0.0-beta3. Users are advised to upgrade. There are no known workarounds for this vulnerability.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 02/16/2025
The vulnerability identified as CVE-2023-39351 represents a critical null pointer dereference flaw within FreeRDP's RemoteFX implementation that directly impacts the stability and reliability of remote desktop connections. This issue manifests specifically within the rfx_process_message_tileset function where the application attempts to allocate memory for tiles using the rfx_allocate_tiles function based on the numTiles parameter. The vulnerability stems from inadequate error handling during the tile initialization process, where the allocation routine may fail to properly initialize all allocated tile structures, resulting in NULL pointers that subsequently get dereferenced during normal processing operations. This type of vulnerability falls under the CWE-476 category of NULL Pointer Dereference, which is classified as a fundamental memory safety issue that can lead to application crashes and potentially more severe consequences if exploited in certain contexts.
The operational impact of this vulnerability extends beyond simple application instability, as it can disrupt critical remote desktop services that organizations rely upon for system administration, remote work capabilities, and technical support operations. When the null pointer dereference occurs during RemoteFX tile processing, the application experiences an immediate crash that terminates the remote desktop session and forces users to reconnect, creating significant disruption in productivity and service availability. The vulnerability affects the core RDP functionality that enables high-quality graphics rendering over remote connections, making it particularly concerning for environments where visual fidelity and performance are essential. According to the ATT&CK framework, this vulnerability could be leveraged as part of a broader attack chain targeting remote desktop services, potentially enabling denial of service attacks against critical infrastructure or creating opportunities for further exploitation.
The technical exploitation of this vulnerability requires specific conditions where the tile allocation process fails during initialization, typically occurring when the application encounters memory constraints or processing errors during the RemoteFX graphics handling phase. The flaw demonstrates poor defensive programming practices where the application does not adequately validate that all allocated memory structures have been successfully initialized before proceeding with operations that assume valid data structures. This particular issue affects all versions of FreeRDP prior to 2.11.0 and 3.0.0-beta3, representing a significant portion of the user base that would be vulnerable to this crash condition. The lack of known workarounds means that organizations cannot implement temporary mitigations while awaiting the official patch deployment, leaving them exposed to potential service disruption until they can upgrade to the patched versions. Security researchers have identified that this vulnerability could potentially be exploited in combination with other weaknesses to create more sophisticated attack vectors, particularly in environments where remote desktop services are exposed to untrusted networks or where multiple vulnerabilities exist within the same codebase. The fix implemented in versions 2.11.0 and 3.0.0-beta3 involves enhanced error checking and proper validation of tile initialization status before proceeding with subsequent processing, thereby preventing the null pointer dereference that previously caused the application to crash.