Heap-based buffer overflow in FreeRDP - CVE-2026-55191
Published: June 15, 2026 / Updated: August 21, 2026
Vulnerability identifier: #VU134508
CSH Severity: High
CVSS v4: 8.4 [CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-55191
CWE-ID: CWE-122
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to execute arbitrary code.
The vulnerability exists due to a heap-based buffer overflow caused by integer overflow in avc444_ensure_buffer in libfreerdp/codec/h264.c when decoding AVC444 GFX frames from a malicious RDP server. A remote attacker can send crafted surface dimensions and H.264 bitstream content to execute arbitrary code.
Exploitation requires a FreeRDP client build using libfreerdp AVC444 decompression with RDPGFX AVC444 negotiated and an H.264 decoder backend enabled.
Affected software
FreeRDP
Fedora
freerdp
Fedora
freerdp
How to mitigate CVE-2026-55191
Install security update from vendor's website.
FreeRDP - update to 3.27.0
freerdp - addressed in versions 3.27.1-1.fc43, 3.27.1-1.fc44
freerdp - addressed in versions 3.27.1-1.fc43, 3.27.1-1.fc44