Researchers at Tencent Zhuque Lab have disclosed “Vghost” (CVE-2026-74580), a flaw in the Linux kernel’s vhost subsystem, which speeds up networking and I/O for virtual machines and containers. A local user who can open a vhost device node (usually /dev/vhost-net or /dev/vhost-vsock) gets reliable read and write access to kernel memory, bypasses KASLR and can become root. The attack is deterministic and needs no lucky timing. The fix was released on August 3, and the full write-up with working demos followed on October 12. There is no public sign of exploitation yet.
A second path is narrower: when a virtual machine’s virtio device sits behind a virtual IOMMU with iommu_platform on and vhost runs in device-IOTLB mode, an untrusted guest can make the host kernel write out of bounds into the host’s QEMU process, which can crash it or redirect it. The bug survived about nine years because two reasonable changes combined: a 2017 cache shortcut (Linux 4.11) and a 2020 change (Linux 5.9) that moved address checking to a later step. The kernel.org CVE team scores it 8.8, while Red Hat (7.3), Amazon (7.8) and Oracle (7.3) score it lower; they disagree on whether the guest-to-host write crosses a trust boundary. Tencent says its Corvus AI multi-agent research system found the bug; that is machine-assisted research, not an AI-driven attack.
How to check if you’re affected
Affected versions are Linux kernels from 4.11 up to 7.2-rc4, though distributions may have backported the fix without changing the version number. Tencent reproduced the local-user-to-root chain on Ubuntu 26.04, RHEL 9.8, Amazon Linux 2023, Microsoft Azure Linux 3.0 and Oracle Linux 10.2.
- Run
uname -rand compare it with your distribution’s CVE-2026-74580 tracker rather than the upstream version alone. Upstream stable branches first fixed in 5.10.265, 5.15.216, 6.1.183, 6.6.152, 6.12.104, 6.18.45, 7.1.9 and 7.2. - Red Hat, Amazon Linux and Oracle Linux have shipped fixes. Ubuntu has fixed 22.04, but as of October 13 still listed its 24.04 and 26.04 kernels as in progress.
- Run
ls -l /dev/vhost-net /dev/vhost-vsock. On four of the five tested images the nodes were world-accessible (mode 0666); on Ubuntu access was limited to the kvm group. - Until you can install a patched kernel and reboot, remove world access to those device nodes and limit the owning group to trusted virtualization services. There is no interim workaround for the guest-to-host escape; only the patched kernel fixes it.