CVE-2025-11234: Qemu-kvm: vnc websocket handshake use-after-free

Vulnerability summary

CVE-2025-11234 is a high (CVSS 7.5) Use After Free vulnerability in qemu. EPSS estimates a 0.86% chance of exploitation in the next 30 days, higher than 58.6% of scored vulnerabilities.

Timeline

1. 03-10-2025
   PublishedVulnerability first disclosed.
2. 09-10-2026
   Last modifiedVulnerability information updated.

Description

A flaw was found in QEMU. If the QIOChannelWebsock object is freed while it is waiting to complete a handshake, a GSource is leaked. This can lead to the callback firing later on and triggering a use-after-free in the use of the channel. This can be abused by a malicious client with network access to the VNC WebSocket port to cause a denial of service during the WebSocket handshake prior to the VNC client authentication.

• CWE-416Use After FreeThe product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.