Reachable assertion in FreeRDP - #VU156171
Published: October 19, 2026
Vulnerability identifier: #VU156171
CSH Severity: Medium
CVSS v4: 6.7 [CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: N/A
CWE-ID: CWE-617
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to cause a denial of service by terminating a connecting FreeRDP client process.
The vulnerability exists due to a reachable assertion in the FreeRDP RemoteFX decoder's rfx_process_message function when processing region rectangle coordinates. A remote attacker can induce a user to connect to a malicious RDP server and negotiate RemoteFX, then send a crafted region rectangle with x = 65535 and a SurfaceBits destination with left = 1 to trigger the assertion that their sum fits in a 16-bit coordinate and abort the client process.
The demonstrated crash requires a client built with WITH_VERBOSE_WINPR_ASSERT=ON.
Affected software
FreeRDP
Remediation
Install security update from vendor's website.
FreeRDP - update to 3.32.2