Cybersecurity
Linux vhost flaw lets users gain root access
Tencent Zhuque Lab said a flaw in Linux's vhost subsystem let local users gain root privileges and, in one virtualisation setup, allowed an untrusted guest to write into the host's QEMU process.
- Tencent Zhuque Lab said the bug was in Linux's vhost subsystem, tracked as CVE-2026-74580 and named Vghost, and that it let a local user read and write kernel memory and gain root access.
- The lab said it fixed the flaw on 3 August and published a write-up on 12 October, and it said there was no public sign of exploitation.
- In a setup with virtio behind a virtual IOMMU and vhost running in device-IOTLB mode, the same bug let an untrusted guest make the host kernel write beyond bounds into QEMU.
- Tencent said the flaw affected Linux kernels from 4.11 through 7.2-rc4 and reproduced the local privilege-escalation chain on Ubuntu 26.04, RHEL 9.8, Amazon Linux 2023, Microsoft Azure Linux 3.0 and Oracle Linux 10.2.
- The kernel.org CVE team rated the issue 8.8 and marked the scope as changed, and Tencent said Corvus AI helped find the flaw.
Tencent Zhuque Lab said the bug sat in Linux's vhost code and could be reached through device nodes such as /dev/vhost-net and /dev/vhost-vsock. It said the problem emerged from two later changes that interacted badly and left stale memory mappings in place.
On the host, the flaw let an unprivileged local user read and write kernel memory, bypass KASLR and obtain root access. Tencent said the attack did not depend on memory grooming or favourable timing.
A second path applied only in a narrower virtualisation setup. With virtio behind a virtual IOMMU, iommu_platform enabled and device-IOTLB mode active, an untrusted guest could trigger the same bug and cause an out-of-bounds write in the host's QEMU process.
Tencent said it reproduced the full local privilege-escalation chain on Ubuntu 26.04, RHEL 9.8, Amazon Linux 2023, Microsoft Azure Linux 3.0 and Oracle Linux 10.2. It said Red Hat, Amazon Linux and Oracle Linux had shipped fixes, while Ubuntu still listed some kernels as in progress on 13 October.
The kernel.org CVE team scored the issue 8.8 and marked the scope as changed, while Red Hat, Amazon and Oracle gave lower scores. Tencent said Corvus AI helped identify the flaw, and the upstream patch credited it with an assisted-by line.
Named in this story
Companies
- Red Hat
- gave the issue a lower score and shipped fixes
Organisations
- Tencent Zhuque Lab
- found the flaw and published the analysis
- kernel.org CVE team
- rated the issue 8.8 and marked the scope as changed
Products and systems
- Linux kernel
- contained the vulnerable code
- vhost subsystem
- was the kernel component with the flaw
- Corvus AI
- helped Tencent's kernel research pipeline
- Ubuntu 26.04
- was one of the kernels Tencent reproduced the local exploit on
- RHEL 9.8
- was one of the kernels Tencent reproduced the local exploit on
- Amazon Linux 2023
- was one of the kernels Tencent reproduced the local exploit on
- Microsoft Azure Linux 3.0
- was one of the kernels Tencent reproduced the local exploit on
- Oracle Linux 10.2
- was one of the kernels Tencent reproduced the local exploit on
- QEMU
- was the host process that a guest could affect
How the source tells it
The article read as a technical security advisory, with measured threat language and practical remediation advice.
- security threat describes root access and guest-to-host memory corruption as direct outcomes
- patch urgency closes with instructions to restrict device access and install fixed kernels