CVE-2026-55191

FreeRDP is a free implementation of the Remote Desktop Protocol. Prior to 3.27.0, FreeRDP clients that negotiate RDPGFX AVC444 with an H.264 decoder backend calculate the intermediate YUV444 allocation size in libfreerdp/codec/h264.c with 32-bit multiplication in avc444_ensure_buffer. A malicious RDP server can supply surface dimensions for which piDstStride multiplied by padDstHeight wraps to a small nonzero value, causing winpr_aligned_recalloc to allocate an undersized buffer before YUV420CombineToYUV444 writes using the actual stride and rectangle dimensions. This can cause a client crash and may permit code execution through attacker-influenced heap corruption. This issue is fixed in version 3.27.0.

What this means for your business

It affects Freerdp. It matters if your company, or a supplier that handles your data, runs it.
Code showing how to exploit it has been published, but real attacks have not been confirmed.
An attacker can use it remotely, over a network, without a login, and without anyone at your company clicking anything.
FIRST's prediction model gives it a 0.6% chance of attack attempts being seen in the next 30 days, ranking above 46% of all known flaws.

What to do

1Check whether your company or your suppliers run Freerdp, and which version. The affected versions are listed further down this page.
2If you do, apply the vendor's fix. A patch or vendor advisory has been published.

Not sure if your company is exposed?

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Scoring

CVSS: 9.8 (v3.1)
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS v4: 8.7
Weakness: CWE-122
Assigned by: security-advisories@github.com

Dates

Published: 2026-08-19
Last modified: 2026-09-22
Sources: NVD

Affected products

Freerdp Freerdp- 3.27.0

As listed in the NVD configuration data. Not a statement about your estate.