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

Summary: A flaw in the Linux kernel's KVM virtualization code for ARM64, tracked as CVE-2026-89775, lets a guest read and write freed host kernel memory 64 bits at a time when a size calculation comes out as zero and a TLB invalidation is skipped. Researcher Hyunwoo Kim, who disclosed it on September 16, says a guest can use it to escape to the host and run code there, and it is fixed in Linux 6.18.51, 7.2.5, and 7.3-rc1.
Why it matters: The attack path requires nested virtualization, an experimental boot-time mode that is off by default on ARM64 and not offered on AWS's or Google Cloud's standard ARM instances, but on systems where any user can open /dev/kvm - Red Hat Enterprise Linux by default - a local user could build a guest and use the same bug to gain root.

Read the original at The Hacker News ↗

Topics: Vulnerabilities & Patching
Mentions: CVE-2026-89775
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