Vghost: AI-Found Linux Kernel Flaw Lets Local Users Gain Root and Can Expose Virtual Machine Hosts

Researchers at Tencent Zhuque Lab have disclosed a flaw in vhost, the part of the Linux kernel that speeds up network and other input/output for virtual machines and containers. Tracked as CVE-2026-74580 and named Vghost, it affects nearly a decade of kernel versions. On a host, an unprivileged local user can read and write kernel memory and escalate to root. The attack is deterministic, so it needs no lucky timing.

A second attack is narrower. It applies when a virtual machine's virtio device sits behind a virtual IOMMU with iommu_platform turned on, and vhost runs in device-IOTLB mode. In that setup, an untrusted guest can make the host kernel write out of bounds into the host's QEMU process, which could let the guest take control of that process or crash it.

The cause is a cache that vhost keeps of memory mappings. A cache hit is treated as proof that a region was already checked, but the cache is not cleared when certain commands change a live queue's addresses or size. The kernel can then use an old mapping for new addresses and copy data outside the intended region. A fix was released on August 3, and a full write-up with working demos followed on October 12. There is no public sign of exploitation yet, but the published demos may raise the risk. This summary covers only the opening of the source article.