CVE-2025-11234 is a use-after-free vulnerability identified in the QEMU virtualization software, specifically within the QIOChannelWebsock object used for handling VNC WebSocket connections. The issue arises when the QIOChannelWebsock object is freed while it is still waiting to complete the WebSocket handshake process. This premature freeing leads to a GSource resource leak, which causes the callback associated with the handshake to fire later on referencing the freed memory. This use-after-free condition can be exploited by a remote attacker with network access to the VNC WebSocket port to trigger a denial of service (DoS) by crashing or destabilizing the QEMU process before the VNC client authentication occurs. The vulnerability affects Red Hat Enterprise Linux 10 version 2.6.0, which bundles QEMU. The CVSS v3.1 score is 7.5 (high), reflecting the network vector (AV:N), low attack complexity (AC:L), no privileges required (PR:N), no user interaction (UI:N), unchanged scope (S:U), no confidentiality or integrity impact (C:N/I:N), but high impact on availability (A:H). There are no known exploits in the wild at the time of publication, but the flaw presents a clear risk to availability of virtualized services relying on VNC over WebSocket. The vulnerability is particularly relevant for environments exposing VNC WebSocket ports to untrusted networks. Since the flaw occurs prior to authentication, it can be triggered by unauthenticated remote attackers. The vulnerability was published on October 3, 2025, and is assigned to Red Hat as the vendor project. No patches or exploit indicators were provided in the initial disclosure, emphasizing the need for proactive mitigation.

This vulnerability primarily impacts the availability of virtual machines managed by QEMU on Red Hat Enterprise Linux 10 systems using the affected version. A successful exploitation results in denial of service by crashing or destabilizing the QEMU process during the VNC WebSocket handshake phase, potentially causing downtime for hosted services or applications. For European organizations, especially those relying on virtualization for critical infrastructure, cloud services, or enterprise applications, this could lead to service interruptions and operational disruptions. Since the attack requires only network access to the VNC WebSocket port and no authentication, exposed services are at significant risk. The lack of confidentiality or integrity impact reduces the risk of data breaches but does not diminish the operational impact. Organizations with remote management or monitoring tools that use VNC over WebSocket are particularly vulnerable. The vulnerability could be leveraged as part of a larger attack chain to degrade service availability or distract security teams. Given the high adoption of Red Hat Enterprise Linux in European government, finance, and industrial sectors, the potential impact is considerable.

1. Apply patches or updates from Red Hat as soon as they become available to address CVE-2025-11234. 2. Restrict network access to VNC WebSocket ports using firewalls, VPNs, or network segmentation to limit exposure to trusted hosts only. 3. Disable or avoid using VNC WebSocket interfaces if not strictly necessary, or replace with more secure remote management protocols. 4. Monitor network traffic and logs for unusual connection attempts or handshake failures on VNC WebSocket ports to detect potential exploitation attempts. 5. Implement rate limiting or connection throttling on VNC WebSocket services to mitigate denial of service attempts. 6. Employ intrusion detection/prevention systems (IDS/IPS) tuned to detect anomalies in WebSocket handshake sequences. 7. Regularly review and update virtualization host security configurations and hardening guidelines. 8. Educate system administrators about the risks associated with exposing VNC WebSocket ports to untrusted networks. These measures, combined with timely patching, will reduce the attack surface and mitigate the risk posed by this vulnerability.