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

The record

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A flaw in the Linux kernel on ARM64 processors allows a guest virtual machine to read and write host kernel memory when nested virtualization is enabled.
The vulnerability, tracked as CVE-2026-89775, stems from a missed cache invalidation during memory management for nested hypervisors.
Local attackers can potentially exploit this to escape a virtual machine and execute code on the host.
Patching is currently underway across major Linux distributions.
This security issue only impacts systems where nested virtualization has been explicitly configured by the user.

Monitoring for potential exploit code publication or observed exploitation in the wild.
Deployment of vendor-specific kernel updates across affected cloud and local environments.

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“a guest can use this to escape to the host, breaking out of its own virtual machine to run code on the underlying machine.”
[1]The Hacker News3h agoOpen at the quote ↗
In the article
…writable, and the guest can read and write it 64 bits at a time, with no hardware trap to hand control back to the host. Hyunwoo Kim, the security researcher who reported the flaw and disclosed it on September 16, says a guest can use this to escape to the host, breaking out of its own virtual machine to run code on the underlying machine. No exploit code has been published, and there is no sign the flaw has been used in an attack. The kernel's own record lists the affected code as present from Linux 6.16. But the author tagged the fix against a later…

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Named United States · Amazon Linux · Debian · KVM · Linux kernel · Red Hat · Ubuntu · Hyunwoo Kim

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