# CVE-2025-11234: Qemu-kvm: vnc websocket handshake use-after-free > A malicious client can cause a denial of service in QEMU's VNC WebSocket handshake via a use-after-free vulnerability before authentication. - **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 3 Oct 2025 - **Updated:** 9 Oct 2026 - **Also known as:** ALSA-2026:1831, ALSA-2026:18772, ALSA-2026:5578, AZL-68193, AZL-68202, CLSA-2026-1779580341, CLSA-2026-1779581056, DEBIAN-CVE-2025-11234, GHSA-hm8v-8c3v-cxfq, OESA-2026-1263, RHSA-2025:23228, RHSA-2026:1831, RHSA-2026:18772, RHSA-2026:22147, RHSA-2026:3077, RHSA-2026:3165, RHSA-2026:5578, RLSA-2026:1831, RLSA-2026:18772, RLSA-2026:5578, SUSE-SU-2026:0356-1, SUSE-SU-2026:0436-1, UBUNTU-CVE-2025-11234 ## What is CVE-2025-11234? CVE-2025-11234 is a high-severity use after free vulnerability in Red Hat Enterprise Linux 10, published on 3 Oct 2025. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official 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. Weakness: CWE-416 (Use After Free) ## Which versions are affected by CVE-2025-11234? | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `qemu-guest-agent` | AlmaLinux:10 | All versions | 18:10.0.0-14.el10_1.5.alma.1 | | `qemu-img` | AlmaLinux:10 | All versions | 18:10.0.0-14.el10_1.5.alma.1 | | `qemu-kvm` | AlmaLinux:10 | All versions | 18:10.0.0-14.el10_1.5.alma.1 | | `qemu-kvm-audio-pa` | AlmaLinux:10 | All versions | 18:10.0.0-14.el10_1.5.alma.1 | | `qemu-kvm-block-blkio` | AlmaLinux:10 | All versions | 18:10.0.0-14.el10_1.5.alma.1 | | `qemu-kvm-block-curl` | AlmaLinux:10 | All versions | 18:10.0.0-14.el10_1.5.alma.1 | | `qemu-kvm-block-rbd` | AlmaLinux:10 | All versions | 18:10.0.0-14.el10_1.5.alma.1 | | `qemu-kvm-common` | AlmaLinux:10 | All versions | 18:10.0.0-14.el10_1.5.alma.1 | | `qemu-kvm-core` | AlmaLinux:10 | All versions | 18:10.0.0-14.el10_1.5.alma.1 | | `qemu-kvm-device-display-virtio-gpu` | AlmaLinux:10 | All versions | 18:10.0.0-14.el10_1.5.alma.1 | | `qemu-kvm-device-display-virtio-gpu-ccw` | AlmaLinux:10 | All versions | 18:10.0.0-14.el10_1.5.alma.1 | | `qemu-kvm-device-display-virtio-gpu-pci` | AlmaLinux:10 | All versions | 18:10.0.0-14.el10_1.5.alma.1 | | `qemu-kvm-device-display-virtio-vga` | AlmaLinux:10 | All versions | 18:10.0.0-14.el10_1.5.alma.1 | | `qemu-kvm-device-usb-host` | AlmaLinux:10 | All versions | 18:10.0.0-14.el10_1.5.alma.1 | | `qemu-kvm-device-usb-redirect` | AlmaLinux:10 | All versions | 18:10.0.0-14.el10_1.5.alma.1 | | `qemu-kvm-docs` | AlmaLinux:10 | All versions | 18:10.0.0-14.el10_1.5.alma.1 | | `qemu-kvm-tools` | AlmaLinux:10 | All versions | 18:10.0.0-14.el10_1.5.alma.1 | | `qemu-kvm-ui-egl-headless` | AlmaLinux:10 | All versions | 18:10.0.0-14.el10_1.5.alma.1 | | `qemu-kvm-ui-opengl` | AlmaLinux:10 | All versions | 18:10.0.0-14.el10_1.5.alma.1 | | `qemu-pr-helper` | AlmaLinux:10 | All versions | 18:10.0.0-14.el10_1.5.alma.1 | | `SLOF` | AlmaLinux:8 | All versions | 20210217-2.module_el8.10.0+3768+dfd76e10 | | `hivex` | AlmaLinux:8 | All versions | 1.3.18-23.module_el8.6.0+2880+7d9e3703 | | `hivex` | AlmaLinux:8 | All versions | 1.3.18-23.module_el8.6.0+3161+a07c0ea5 | | `hivex-devel` | AlmaLinux:8 | All versions | 1.3.18-23.module_el8.6.0+2880+7d9e3703 | | `hivex-devel` | AlmaLinux:8 | All versions | 1.3.18-23.module_el8.6.0+3161+a07c0ea5 | | `libguestfs` | AlmaLinux:8 | All versions | 1:1.44.0-9.module_el8.7.0+3493+5ed0bd1c.alma | | `libguestfs-appliance` | AlmaLinux:8 | All versions | 1:1.44.0-9.module_el8.7.0+3493+5ed0bd1c.alma | | `libguestfs-bash-completion` | AlmaLinux:8 | All versions | 1:1.44.0-9.module_el8.7.0+3493+5ed0bd1c.alma | | `libguestfs-devel` | AlmaLinux:8 | All versions | 1:1.44.0-9.module_el8.7.0+3493+5ed0bd1c.alma | | `libguestfs-gfs2` | AlmaLinux:8 | All versions | 1:1.44.0-9.module_el8.7.0+3493+5ed0bd1c.alma | | `libguestfs-gobject` | AlmaLinux:8 | All versions | 1:1.44.0-9.module_el8.7.0+3493+5ed0bd1c.alma | | `libguestfs-gobject-devel` | AlmaLinux:8 | All versions | 1:1.44.0-9.module_el8.7.0+3493+5ed0bd1c.alma | | `libguestfs-inspect-icons` | AlmaLinux:8 | All versions | 1:1.44.0-9.module_el8.7.0+3493+5ed0bd1c.alma | | `libguestfs-java` | AlmaLinux:8 | All versions | 1:1.44.0-9.module_el8.7.0+3493+5ed0bd1c.alma | | `libguestfs-java-devel` | AlmaLinux:8 | All versions | 1:1.44.0-9.module_el8.7.0+3493+5ed0bd1c.alma | | `libguestfs-javadoc` | AlmaLinux:8 | All versions | 1:1.44.0-9.module_el8.7.0+3493+5ed0bd1c.alma | | `libguestfs-man-pages-ja` | AlmaLinux:8 | All versions | 1:1.44.0-9.module_el8.7.0+3493+5ed0bd1c.alma | | `libguestfs-man-pages-uk` | AlmaLinux:8 | All versions | 1:1.44.0-9.module_el8.7.0+3493+5ed0bd1c.alma | | `libguestfs-rescue` | AlmaLinux:8 | All versions | 1:1.44.0-9.module_el8.7.0+3493+5ed0bd1c.alma | | `libguestfs-rsync` | AlmaLinux:8 | All versions | 1:1.44.0-9.module_el8.7.0+3493+5ed0bd1c.alma | ## How do I fix CVE-2025-11234? Apply the vendor's patch. ## Is CVE-2025-11234 being exploited? There is no known exploitation of CVE-2025-11234 in the wild and no public exploit code. ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2025-11234 and fix it if it is affected. What it is: CVE-2025-11234 is a high-severity use after free vulnerability in Red Hat Enterprise Linux 10, published on 3 Oct 2025. An attacker can exploit it over the internet without logging in, with no action from the victim. Exploitation: There is no known exploitation of CVE-2025-11234 in the wild and no public exploit code. Affected product: Red Hat Enterprise Linux 10. No package-level version data is available, so check the vendor advisory linked from the reference page. Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2025-11234/ (Markdown: https://insights.sbomify.com/CVE-2025-11234/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2025-11234 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-11234 - OSV: https://osv.dev/vulnerability/CVE-2025-11234 --- From sbomify Insights: https://insights.sbomify.com/CVE-2025-11234/ Summaries are generated and may contain mistakes; the official description above is the record.