CVE-2026-26965 — FreeRDP has Out-of-bounds Write

Description (CNA)

FreeRDP is a free implementation of the Remote Desktop Protocol. Prior to version 3.23.0, in the RLE planar decode path, `planar_decompress_plane_rle()` writes into `pDstData` at `((nYDst+y) * nDstStep) + (4*nXDst) + nChannel` without verifying that `(nYDst+nSrcHeight)` fits in the destination height or that `(nXDst+nSrcWidth)` fits in the destination stride. When `TempFormat != DstFormat`, `pDstData` becomes `planar->pTempData` (sized for the desktop), while `nYDst` is only validated against the **surface** by `is_within_surface()`. A malicious RDP server can exploit this to perform a heap out-of-bounds write with attacker-controlled offset and pixel data on any connecting FreeRDP client. The OOB write reaches up to 132,096 bytes past the temp buffer end, and on the brk heap (desktop ≤ 128×128), an adjacent `NSC_CONTEXT` struct's `decode` function pointer is overwritten with attacker-controlled pixel data — control-flow–relevant corruption (function pointer overwritten) demonstrated under deterministic heap layout (`nsc->decode = 0xFF414141FF414141`). Version 3.23.0 fixes the vulnerability.

Affected (CNA)

Vendor / product	Versions
FreeRDP / FreeRDP	affected < 3.23.0

CWE

CWE-787

References

ADP enrichment

CISA-ADP

No English description supplied.

No references supplied.

redhat-SADP

A flaw was found in FreeRDP, a free implementation of the Remote Desktop Protocol (RDP). A malicious RDP server can exploit a heap out-of-bounds write vulnerability in the `planar_decompress_plane_rle()` function. This vulnerability allows the server to write past the end of a temporary buffer, potentially overwriting critical data such as function pointers. This can lead to arbitrary code execution on the connecting FreeRDP client.