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

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.

This CVE has been rated as Moderate because it only affects the WebSocket protocol for communication (the VNC raw TCP socket is not affected) and the use of QEMU's in-process WebSocket feature is fairly niche. Red Hat severity: Moderate — CVSS 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).

Weakness: CWE-416.

Affected products named by the advisory: Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support; Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On; Red Hat Enterprise Linux 8.8 Telecommunications Update Service; and 10 more.