CVE-2026-74580: Linux vhost flaw gives local users root
Vghost kernel bug can also write from a guest into the host

CVE-2026-74580: Linux vhost flaw gives local users root

CVE-2026-74580, named Vghost, is a flaw in the Linux vhost subsystem. A local user can read and write kernel memory and become root. In one virtualization setup, a guest can write into the host's QEMU process.

What happened

Tencent Zhuque Lab found the bug with Corvus, its multi-agent research system, and landed a fix on 3 August. The public write-up, with working demos, followed on 12 October. There is no public sign of exploitation.

vhost speeds up I/O for virtual machines and containers. A local user reaches it through a device node, usually /dev/vhost-net or /dev/vhost-vsock. A stale address cache is not cleared when the ring is resized while the queue is live. After a cache hit, the kernel copies data using the old mapping, with no bounds check.

The bug sat in the tree for about nine years. A 2017 change added the cache. A 2020 change moved the address check to a later step that the cache then skips. The local attack is deterministic: no heap grooming and no race.

The guest-to-host path is narrower. It needs a virtio device behind a virtual IOMMU with iommu_platform on, and vhost in device-IOTLB mode. From there a guest can overwrite a function pointer in the host QEMU process. Kernel.org scores the issue 8.8 with changed scope. Red Hat scores it 7.3.

Who is affected

  • Linux kernels from 4.11 through 7.2-rc4, until a build that contains commit de845981da67 is installed.
  • Hosts where /dev/vhost-net or /dev/vhost-vsock is world-accessible. Tencent reproduced local root on Ubuntu 26.04, RHEL 9.8, Amazon Linux 2023, Azure Linux 3.0, and Oracle Linux 10.2. On Ubuntu the node was limited to the kvm group. On the other four it was mode 0666.
  • Hypervisors that place virtio behind a virtual IOMMU with device IOTLB. That path has no workaround short of the patched kernel.

What to do now

Install a kernel that contains the fix and reboot. Until then, remove world access to /dev/vhost-net and /dev/vhost-vsock and treat membership of the owning group as a privilege.

First fixed upstream stable versions include 5.10.265, 5.15.216, 6.1.183, 6.6.152, 6.12.104, 6.18.45, and 7.1.9. Vendors may backport without changing the version string, so check the vendor advisory, not only the kernel number. Red Hat, Amazon Linux, and Oracle have shipped fixes. As of 13 October, Ubuntu had fixed 22.04 and still listed 24.04 and 26.04 as in progress.

This is a local bug, not a remote worm. Prioritise multi-tenant hypervisors, container hosts, and any box where untrusted users can open a vhost device. A guest escape has no interim mitigation.

Source: The Hacker News, 14 October 2026, AI-Found Linux Kernel Flaw Gives Local Users Root, and Can Break a Guest Out to the Host.

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Next step: If this is on your network or a client's, ask Matthews Enterprises to check exposure.

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