New Linux Kernel Flaw Gives ARM64 KVM Guests Read-Write Access to Host Memory
AI-summarised brief · reviewed before publication
A new Linux kernel vulnerability, CVE‑2026‑89775, affects the KVM virtualization subsystem on ARM64 platforms with nested virtualization enabled. The flaw arises from an incorrect size calculation that skips a TLB invalidation, leaving a freed host memory page mapped and writable to a guest VM. Researchers demonstrate that a malicious guest can read and write host kernel memory, enabling a VM escape to execute code on the host. The bug is present in mainline kernels from version 6.16 onward, but the exploitable behavior appears from 6.17. Fixes are included in Linux 6.18.51, 7.2.5 and 7.3‑rc1; distributions are rolling out patches at varying schedules. Exploitation requires the experimental nested‑virtualization mode, which is disabled by default on ARM64, and no public exploit code exists.
💡 Why It Matters
- · It reveals that even rarely used ARM64 nested‑virtualization can break the isolation guarantees of containers and VMs, exposing cloud providers and multi‑tenant systems to direct host compromise.
