CVE-2026-26955

A flaw was found in FreeRDP, a free implementation of the Remote Desktop Protocol (RDP). A malicious RDP server can exploit a heap buffer overflow vulnerability by sending a specially crafted graphics command to a FreeRDP client. This allows the server to write data outside of its intended memory region, potentially leading to arbitrary code execution on the client system. The vulnerability occurs because the client does not properly validate the dimensions of incoming graphics commands.

A malicous RDP server may lead a heap buffer overflow in FreeRDP when the client is using the GDI surface pipeline. This happens when the server send a maliciously crafted RDPGFX ClearCodec command. When interpreting the command FreeRDP fails to validate the whether rectangle described by it falls within the destination surface dimension allowing the attacker to overwrite the surface data buffer without any boundaries check. Depending on the memory layout of the freerdp client's process it's possible to corrupt adjacent points leading to a remote code execution or force the freerdp client to crash.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

To mitigate this issue, avoid connecting to untrusted or unverified RDP servers. Users should only establish RDP connections with known and trusted servers. If connecting to untrusted servers is unavoidable, consider using a sandbox environment or a dedicated, isolated system for such connections to limit potential impact.