CVE-2023-40187 in FreeRDP
Summary
by MITRE • 09/01/2023
FreeRDP is a free implementation of the Remote Desktop Protocol (RDP), released under the Apache license. Affected versions of the 3.x beta branch are subject to a Use-After-Free issue in the `avc420_ensure_buffer` and `avc444_ensure_buffer` functions. If the value of `piDstSize[x]` is 0, `ppYUVDstData[x]` will be freed. However, in this case `ppYUVDstData[x]` will not have been updated which leads to a Use-After-Free vulnerability. This issue has been addressed in version 3.0.0-beta3. Users of the 3.x beta releases are advised to upgrade. There are no known workarounds for this vulnerability.
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Analysis
by VulDB Data Team • 09/29/2023
The vulnerability identified as CVE-2023-40187 affects FreeRDP, a widely-used open-source implementation of the Remote Desktop Protocol that enables remote desktop connections across various platforms. This security flaw exists within the 3.x beta branch of the software, specifically targeting the video processing components responsible for handling YUV buffer management during video frame processing. The issue manifests in two critical functions: `avc420_ensure_buffer` and `avc444_ensure_buffer`, which are essential for managing video data during remote desktop sessions. The vulnerability stems from improper memory management practices that create dangerous conditions during buffer allocation and deallocation processes.
The technical flaw occurs when the value of `piDstSize[x]` equals zero, triggering a premature memory deallocation scenario. In this specific condition, the `ppYUVDstData[x]` pointer gets freed from memory while simultaneously remaining in a state where it has not been properly reassigned or updated. This creates a classic use-after-free vulnerability where a subsequent access to the freed memory location could result in undefined behavior, potential application crashes, or more critically, arbitrary code execution. The vulnerability is particularly concerning because it occurs during normal video processing operations within RDP sessions, making it exploitable during typical remote desktop usage scenarios. This type of vulnerability is categorized under CWE-416 as "Use After Free" and represents a fundamental memory safety issue that violates standard software development practices for resource management.
The operational impact of this vulnerability extends beyond simple application instability to potentially enable remote code execution attacks against systems running affected FreeRDP versions. Attackers could exploit this flaw by crafting malicious RDP connections that trigger the specific memory management condition, potentially leading to complete system compromise. The vulnerability affects all users of the 3.x beta releases, which were intended as testing versions but have been deployed in production environments, making the impact widespread. Given that FreeRDP is commonly used for enterprise remote desktop solutions, the potential for exploitation increases significantly in corporate environments where RDP is heavily utilized. This vulnerability aligns with ATT&CK technique T1190 "Exploit Public-Facing Application" as it represents an exploitable condition in a widely-deployed network service component.
Organizations utilizing FreeRDP in their remote desktop infrastructure should immediately prioritize upgrading to version 3.0.0-beta3 or later, which contains the necessary patches to address this memory management flaw. The vulnerability does not have any known workarounds since it resides in core memory management functions that cannot be bypassed without fundamentally altering the software behavior. System administrators should conduct immediate inventory checks to identify all systems running affected FreeRDP versions and implement the upgrade process as a critical security measure. The patch addresses the root cause by ensuring proper pointer management and memory allocation validation before deallocation occurs, preventing the scenario where freed memory could be accessed subsequently. Security teams should monitor for any indicators of exploitation attempts and consider implementing network-based detection measures to identify potential attack traffic targeting this specific vulnerability.