CVE-2026-67300 FreeRDP before 3.29.0 Use-After-Free via async message proxy
A malicious RDP server can trigger a use-after-free in FreeRDP clients with async updates enabled, leading to memory corruption or crashes.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-67300?
CVE-2026-67300 is a high-severity use after free vulnerability in FreeRDP, published on 1 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
FreeRDP before 3.29.0 contains client-side heap use-after-free vulnerabilities in the async update message proxy for RAIL WINDOW_STATE_ORDER and NOTIFY_ICON_STATE_ORDER when AsyncUpdate is enabled. When a malicious or compromised RDP server sends crafted update orders, the message proxy shallow-copies structures containing nested parser-owned pointers (e.g., titleInfo.string, windowRects, visibilityRects, icon buffers). The parser frees those nested buffers after the callback returns, so the queued async message later dispatches stale pointers, potentially causing memory corruption or a client crash.
Weakness: CWE-416
Which versions are affected by CVE-2026-67300?
How do I fix CVE-2026-67300?
Upgrade to a fixed version.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-67300 being exploited?
There is no known exploitation of CVE-2026-67300 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-67300, GHSA-33gg-h66j-3697, GHSA-hp6g-g26j-5q54, UBUNTU-CVE-2026-67300.