CVE-2023-39353 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 are subject to a missing offset validation leading to Out Of Bound Read. In the `libfreerdp/codec/rfx.c` file there is no offset validation in `tile->quantIdxY`, `tile->quantIdxCb`, and `tile->quantIdxCr`. As a result crafted input can lead to an out of bounds read access which in turn will cause 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-2023-39353 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 RFX (RemoteFX) codec implementation in the libfreerdp/codec/rfx.c file, specifically targeting the handling of quantization indices for Y, Cb, and Cr color components during image compression. The vulnerability represents a critical out-of-bounds read condition that occurs when the software fails to validate offset values before accessing memory locations, creating a potential avenue for denial-of-service attacks and information disclosure.
The technical flaw manifests in the absence of proper validation for three critical variables: tile->quantIdxY, tile->quantIdxCb, and tile->quantIdxCr, which are used to store quantization indices for different color components in the RFX image encoding process. When processing maliciously crafted RDP packets containing specially constructed tile data, the application reads from memory locations that are outside the intended bounds of the allocated arrays or buffers. This missing validation creates a scenario where an attacker can manipulate input data to cause the software to access memory that it should not be accessing, leading to unpredictable behavior and system instability.
The operational impact of this vulnerability extends beyond simple system crashes, as it represents a fundamental security weakness that could be exploited in various attack scenarios. While the primary consequence is a crash that renders the FreeRDP service unavailable, the vulnerability also presents potential information disclosure risks since out-of-bounds reads may expose sensitive memory contents to attackers. The vulnerability affects all versions of FreeRDP prior to 2.11.0 and 3.0.0-beta3, making it particularly concerning for organizations that rely on older versions of the software for remote desktop connectivity. This flaw falls under the CWE-129 weakness category, which specifically addresses insufficient validation of length of input buffers, and aligns with ATT&CK technique T1210 for exploitation of remote services.
The remediation strategy focuses entirely on upgrading to patched versions of FreeRDP, as no workarounds are available for this particular vulnerability. Organizations should prioritize updating their FreeRDP installations to versions 2.11.0 or 3.0.0-beta3 to eliminate the risk of exploitation. Security teams should implement comprehensive monitoring for any attempts to exploit this vulnerability, particularly in environments where FreeRDP is used for remote desktop access. The vulnerability demonstrates the importance of proper input validation in cryptographic and codec implementations, where memory safety issues can have cascading effects on system stability and security. Given that FreeRDP is commonly used in enterprise environments for remote access solutions, the impact of this vulnerability extends to numerous organizations that must ensure their remote desktop infrastructure remains secure against such memory safety issues.