New Linux Kernel Flaw Gives ARM64 KVM Guests Read-Write Access to Host Memory

A critical flaw in the Linux kernel's KVM virtualization layer for ARM64 processors (CVE-2026-89775) allows a malicious or compromised guest virtual machine to read and write directly to host kernel memory, effectively breaking the isolation boundary that hypervisors depend upon. This type of guest-to-host escape is among the most severe classes of virtualization vulnerabilities, as it can allow an attacker who controls a single tenant VM to compromise the entire host and every other VM running on it. The vulnerability is compounded by the fact that nested virtualization — a feature often enabled for development or cloud-on-cloud scenarios — expands the attack surface significantly. Because distribution-specific patch schedules vary, many production systems may remain exposed long after upstream fixes are available, widening the window of exploitation.