CVE-2023-39356 in FreeRDP
Summary
by MITRE • 09/01/2023
FreeRDP is a free implementation of the Remote Desktop Protocol (RDP), released under the Apache license. In affected versions a missing offset validation may lead to an Out Of Bound Read in the function `gdi_multi_opaque_rect`. In particular there is no code to validate if the value `multi_opaque_rect->numRectangles` is less than 45. Looping through `multi_opaque_rect->`numRectangles without proper boundary checks can lead to Out-of-Bounds Read errors which will likely lead to a 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.
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Analysis
by VulDB Data Team • 02/16/2025
The vulnerability identified as CVE-2023-39356 affects FreeRDP, a widely-used open-source implementation of Microsoft's Remote Desktop Protocol that enables remote desktop connections across various platforms. This security flaw resides within the graphical subsystem of FreeRDP, specifically in the function gdi_multi_opaque_rect which handles multi-rectangle opaque drawing operations. The issue represents a classic buffer overread condition that occurs when processing remote desktop protocol packets containing graphical operations, making it particularly concerning for environments where remote desktop services are extensively utilized.
The technical flaw manifests as a missing input validation check for the numRectangles parameter within the gdi_multi_opaque_rect function. According to CWE-129, this constitutes an insufficient validation of the length or count of input data, specifically failing to validate that multi_opaque_rect->numRectangles is less than 45 before proceeding with array traversal operations. The absence of boundary checking allows an attacker to craft malicious RDP packets that contain an excessive number of rectangles, causing the software to read beyond allocated memory boundaries. This particular implementation flaw falls under the ATT&CK technique T1210 - Exploitation of Remote Services, as it represents a vulnerability in networked remote desktop services that can be exploited through crafted protocol messages.
The operational impact of this vulnerability extends beyond simple service disruption, as the out-of-bounds read conditions typically result in application crashes and potential denial of service scenarios for legitimate users. In enterprise environments where FreeRDP serves as a critical component for remote access and administration, such a vulnerability could lead to significant operational disruptions and may be exploited by malicious actors to gain unauthorized access to systems. The vulnerability affects multiple versions of FreeRDP, with the issue being resolved in versions 2.11.0 and 3.0.0-beta3, highlighting the importance of timely security updates in maintaining secure remote desktop environments. Organizations utilizing FreeRDP for remote desktop connections should prioritize upgrading to patched versions to prevent exploitation, as no effective workarounds exist for this particular vulnerability that could allow attackers to leverage the missing validation to crash services or potentially execute arbitrary code through memory corruption attacks.