CVE-2025-11234
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedA 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceA use-after-free vulnerability exists in QEMU's QIOChannelWebsock implementation where the object can be freed while awaiting handshake completion, causing a GSource leak. The leaked GSource fires later, triggering the use-after-free when the channel is accessed. This occurs during the WebSocket handshake prior to VNC client authentication.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify QEMU installation and versionRun 'qemu-system-x86_64 --version' or 'qemu-img --version' to determine the installed QEMU version. Compare this version against any available fixed versions for CVE-2025-11234.Affected if QEMU version is unpatched and falls within the vulnerable range
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Verify VNC server is enabled in QEMUCheck QEMU command-line arguments or VM configuration files for '-vnc' option. Look for configurations like '-vnc :5900' or '-vnc 0.0.0.0:5900,websocket' which enable VNC with WebSocket support.Affected if VNC server is configured with WebSocket support (the 'websocket' option is present in the VNC configuration)
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Inspect listening network ports for VNC WebSocketRun 'netstat -tlnp' or 'ss -tlnp' and look for ports in the 5700-5800 range (WebSocket VNC typically uses port 5700+). Also check for any port configured with websocket in the service definition.Affected if A VNC WebSocket listener is active and bound to a network interface accessible from untrusted networks
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Confirm QIOChannelWebsock module is loadedCheck QEMU process status or module list. On systems using libvirt, inspect the domain XML for '<graphics type='vnc' websocket='1'/>' or similar WebSocket-enabled graphics configuration.Affected if The environment uses QEMU with WebSocket-enabled VNC graphics (websocket='1' or 'websocket' option in VNC string)
A user is affected if they run a QEMU version with an unpatched QIOChannelWebsock component and have VNC with WebSocket support enabled and exposed to network access.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataUpdate QEMU to the version containing the fix for this vulnerability. As a compensating control, restrict network access to VNC WebSocket ports to trusted clients only.
- Consultation2.0 h
- Implementation2.0 h
- Testing2.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2025-11234 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2025-11234 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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