Critical severity · published Aug 19, 2026
CVE-2026-55191
FreeRDP: Heap-buffer-overflow write in AVC444 YUV buffer allocation
9.8
CVSS
0.6%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.6% · higher than 49% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
FR
FreeRDP · FreeRDP
< 3.27.0 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-55191
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-55191
Patch
https://github.com/FreeRDP/FreeRDP/commit/97f40b9e766af375f4e41ac6a3f4397d708d249c
Issue Tracking
https://github.com/FreeRDP/FreeRDP/pull/12873
Release Notes
https://github.com/FreeRDP/FreeRDP/releases/tag/3.27.0
Exploit
https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-vx73-w5q6-7jqr
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