FreeRDP up to 3.23.x AVC420/AVC444 clamp out-of-bounds write

Summaryinfo

A vulnerability was found in FreeRDP up to 3.23.x. It has been classified as critical. Affected by this vulnerability is the function clamp of the component AVC420/AVC444. The manipulation leads to out-of-bounds write. This vulnerability is traded as CVE-2026-29774. It is possible to initiate the attack remotely. There is no exploit available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability was found in FreeRDP up to 3.23.x. It has been rated as critical. This issue affects the function clamp of the component AVC420/AVC444. The manipulation with an unknown input leads to a out-of-bounds write vulnerability. Using CWE to declare the problem leads to CWE-787. The product writes data past the end, or before the beginning, of the intended buffer. Impacted is availability. The summary by CVE is:

FreeRDP is a free implementation of the Remote Desktop Protocol. Prior to 3.24.0, a client-side heap buffer overflow occurs in the FreeRDP client's AVC420/AVC444 YUV-to-RGB conversion path due to missing horizontal bounds validation of H.264 metablock regionRects coordinates. In yuv.c, the clamp() function (line 347) only validates top/bottom against the surface/YUV height, but never checks left/right against the surface width. When avc420_yuv_to_rgb (line 67) computes destination and source pointers using rect->left, it performs unchecked pointer arithmetic that can reach far beyond the allocated surface buffer. A malicious server sends a WIRE_TO_SURFACE_PDU_1 with AVC420 codec containing a regionRects entry where left greatly exceeds the surface width (e.g., left=60000 on a 128px surface). The H.264 bitstream decodes successfully, then yuv420_process_work_callback calls avc420_yuv_to_rgb which computes pDstPoint = pDstData + rect->top * nDstStep + rect->left * 4, writing 16-byte SSE vectors 1888+ bytes past the allocated heap region. This vulnerability is fixed in 3.24.0.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-29774 since 03/04/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details of the vulnerability are known, but there is no available exploit.

The vulnerability scanner Nessus provides a plugin with the ID 302240 (Linux Distros Unpatched Vulnerability : CVE-2026-29774), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 3.24.0 eliminates this vulnerability.

The vulnerability is also documented in the databases at Tenable (302240), EUVD (EUVD-2026-12055) and CERT Bund (WID-SEC-2026-0725). Be aware that VulDB is the high quality source for vulnerability data.

Affected

• Amazon Linux 2
• Red Hat Enterprise Linux
• Fedora Linux
• SUSE Linux
• Oracle Linux
• SUSE openSUSE
• RESF Rocky Linux
• Open Source FreeRDP

Productinfo

Type

• Remote Access Software

Name

• FreeRDP

Version

• 3.0
• 3.1
• 3.2
• 3.3
• 3.4
• 3.5
• 3.6
• 3.7
• 3.8
• 3.9
• 3.10
• 3.11
• 3.12
• 3.13
• 3.14
• 3.15
• 3.16
• 3.17
• 3.18
• 3.19
• 3.20
• 3.21
• 3.22
• 3.23

License

• open-source

Website

• Product: https://github.com/FreeRDP/FreeRDP/

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