Bug 2442959 (CVE-2026-26965)

Summary: CVE-2026-26965 freerdp: FreeRDP: Arbitrary code execution via heap out-of-bounds write in RLE planar decode path
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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Priority: high    
Version: unspecifiedKeywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in FreeRDP. A malicious Remote Desktop Protocol (RDP) server can exploit a heap out-of-bounds write vulnerability in the RLE planar decode path. This flaw allows the server to write attacker-controlled data beyond the intended buffer, potentially overwriting critical program data such as function pointers. This could lead to arbitrary code execution on the connecting FreeRDP client.
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Bug Depends On: 2442971, 2442972, 2442973, 2442975, 2442974    
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Description OSIDB Bzimport 2026-02-26 06:01:49 UTC 
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.