CVE-2026-40033 FreeRDP - Heap-buffer-overflow in gdi_CacheToSurface via rectangle validation bypass
Remote attackers can trigger heap-buffer-overflow in FreeRDP via malicious RDP servers, potentially achieving remote code execution or crashing the client.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-40033?
CVE-2026-40033 is a high-severity memory corruption vulnerability in Freerdp Freerdp, published on 26 May 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
FreeRDP before 3.26.0 contains a heap-buffer-overflow vulnerability in gdi_CacheToSurface that allows remote attackers to write out-of-bounds heap memory. The vulnerability occurs because rectangle validation clamps coordinates to UINT16_MAX but performs copy operations using unclamped cache entry dimensions, enabling malicious RDP servers to trigger large out-of-bounds writes and potentially achieve remote code execution or client crash.
Which versions are affected by CVE-2026-40033?
It affects 1 product.
Products include Freerdp Freerdp.
How do I fix CVE-2026-40033?
Upgrade to a fixed version.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-40033 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-40033 exists.
Other vulnerabilities in Freerdp Freerdp
- CVE-2021-37594 Other in n/a
- CVE-2021-37595 Other in n/a
- CVE-2026-67305 FreeRDP Windows Client before 3.29.0 Heap Buffer Overflow via Cliprdr
- CVE-2026-66402 FreeRDP before 3.29.0 TLS Certificate Identity Validation Bypass
- CVE-2026-67289 FreeRDP before 3.29.0 HTTP Proxy Request Injection via Redirection
Sources
Also known as DEBIAN-CVE-2026-40033, GHSA-xmr8-h8p4-932m, UBUNTU-CVE-2026-40033.