CVE-2026-44421: FreeRDP RDPGFX CacheToSurface heap-buffer-overflow via clamped-rectangle validation bypass
FreeRDP is a free implementation of the Remote Desktop Protocol. Prior to 3.26.0, a malicious RDP server can trigger a heap-buffer-overflow write in the FreeRDP client by sending crafted RDPGFX PDUs. The bug is in gdiCacheToSurface: it validates a destination rectangle that is clamped to UINT16MAX, but then performs the copy using the original cacheEntry->width/height. This can cause a large out-of-bounds heap write and may lead to client crashes or code execution. This bug is reachable from a malicious RDP server, but only when the client has RDPGFX enabled. This vulnerability is fixed in 3.26.0.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
FreeRDPto a version that resolves this vulnerability.Fixed in 3.26.0
Event History
Frequently Asked Questions
What is the severity of CVE-2026-44421?
The severity of CVE-2026-44421 is rated as high with a score of 8.8.
How do I fix CVE-2026-44421?
To fix CVE-2026-44421, upgrade to FreeRDP version 3.26.0 or later.
What type of vulnerability is CVE-2026-44421?
CVE-2026-44421 is a heap-buffer-overflow vulnerability in the FreeRDP client.
Who is affected by CVE-2026-44421?
Any user of FreeRDP versions prior to 3.26.0 who connects to a malicious RDP server is affected by CVE-2026-44421.
What can attackers do with CVE-2026-44421?
Attackers can exploit CVE-2026-44421 to execute arbitrary code on the FreeRDP client by sending crafted RDPGFX PDUs.