CVE-2026-26965: freerdp Out-of-bounds Write

Vulnerability summary

CVE-2026-26965 is a high (CVSS 8.8) Out-of-bounds Write vulnerability in freerdp. EPSS estimates a 0.63% chance of exploitation in the next 30 days, higher than 49.1% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 25-02-2026
   PublishedVulnerability first disclosed.
2. 15-07-2026
   Last modifiedVulnerability information updated.

Description

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.

• CWE-787Out-of-bounds WriteThe product writes data past the end, or before the beginning, of the intended buffer.