Vulnerability · Published Aug 19, 2026 · Assigned by GitHub_M

CVE-2026-55191FreeRDP: Heap-buffer-overflow write in AVC444 YUV buffer allocation

High 8.7

In plain English

A high-severity heap buffer overflow in FreeRDP from FreeRDP. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 50% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)8.7High

Exploit odds (30 days)0.6%top 50.1% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official description

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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Alpine:v3.24	freerdp	3.27.1-r0	ALPINE-CVE-2026-55191
Debian:12	freerdp2	no fix listed	DEBIAN-CVE-2026-55191
Debian:13	freerdp3	no fix listed	DEBIAN-CVE-2026-55191
Debian:14	freerdp3	3.27.0+dfsg-1	DEBIAN-CVE-2026-55191
Ubuntu:22.04:LTS	freerdp2	no fix listed	UBUNTU-CVE-2026-55191
Ubuntu:24.04:LTS	freerdp3	3.30.0+dfsg-0ubuntu0.24.04.1	USN-8561-1
Ubuntu:24.04:LTS	freerdp3	3.30.0+dfsg-0ubuntu0.24.04.1	UBUNTU-CVE-2026-55191
Ubuntu:25.10	freerdp3	no fix listed	UBUNTU-CVE-2026-55191
Ubuntu:26.04:LTS	freerdp3	3.30.0+dfsg-0ubuntu0.26.04.1	USN-8561-1
Ubuntu:26.04:LTS	freerdp3	3.30.0+dfsg-0ubuntu0.26.04.1	UBUNTU-CVE-2026-55191

Affected products (as reported)

Vendor	Product	Versions
FreeRDP	FreeRDP	< 3.27.0

Weakness: CWE-122, CWE-190 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

References

https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-vx73-w5q6-7jqr x_refsource_CONFIRM
https://github.com/FreeRDP/FreeRDP/pull/12873 x_refsource_MISC
https://github.com/FreeRDP/FreeRDP/commit/97f40b9e766af375f4e41ac6a3f4397d708d249c x_refsource_MISC
https://github.com/FreeRDP/FreeRDP/releases/tag/3.27.0 x_refsource_MISC