Buffer overflow in Freerdp
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.
Vulnerability class: Buffer Overflow
Published · last modified .
CVSS v3 metric
CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.008 (56.0th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 56th percentile — 56.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.005 · newest: 0.008 · change: +0.004
Affected products
- Freerdp — versions < 3.27.0
Weakness classification (CWE)
References
- github.com/FreeRDP/FreeRDP/security/advisories/GHSA-vx73-w5q6-7jqr (Exploit, Mitigation, Vendor Advisory)
- github.com/FreeRDP/FreeRDP/pull/12873 (Patch, Issue Tracking)
- github.com/FreeRDP/FreeRDP/commit/97f40b9e766af375f4e41ac6a3f4397d708d249c (Patch)
- github.com/FreeRDP/FreeRDP/releases/tag/3.27.0 (Release Notes)
Frequently asked questions
- What is CVE-2026-55191?
- CVE-2026-55191 is a critical-severity vulnerability in Freerdp, classified under Heap-based Buffer Overflow. CVSS score: 9.8/10. Published 2026-08-19.
- How severe is CVE-2026-55191?
- Critical severity. CVSS v3 base score is 9.8 out of 10.