New Linux Kernel Flaw Gives ARM64 KVM Guests Read-Write Access to Host Memory
Linux kernel flaw CVE-2026-89775 lets ARM64 KVM guests read and write freed host memory, enabling guest-to-host escape.
Researcher Hyunwoo Kim disclosed CVE-2026-89775 in the Linux kernel's ARM64 KVM nested virtualization code, which skips a TLB invalidation and leaves freed host memory readable and writable by a guest, enabling escape to the host. The attack is local-only and requires nested virtualization (off by default, needing Armv8.4 FEAT_NV2 hardware); vendors score it 7.8-9.3. Fixed in Linux 6.18.51, 7.2.5, and 7.3-rc1, with RHEL 10 and Ubuntu 26.04 affected; Red Hat offers no workaround. No exploit has been published and no attacks have been observed; it is the fourth KVM guest-to-host escape Kim disclosed this year after Januscape, Zapscape, and ITScape.
- CVE-2026-89775 lets a guest read/write host memory 64 bits at a time with no hardware trap
- Requires local access plus nested virtualization enabled on ARM64, which is not default
- Fixed in Linux 6.18.51, 7.2.5, 7.3-rc1; RHEL 10 and Ubuntu 26.04 kernels affected
- Second abuse path: local users on systems with open /dev/kvm could gain root
- Not in CISA KEV, no PoC published, predicted exploitation below 1%
- CVEs
- CVE-2026-89775
Vulnerabilities mentioned
All| CVE | Vulnerability | CVSS | EPSS | Signals | Published |
|---|---|---|---|---|---|
| CVE-2026-89775 | Improper TLB invalidation in Linux kernel KVM/arm64 risks cross-VM memory exposure | 9.3 | — |
From the original article
4 min read at thehackernews.com
A new flaw in the Linux kernel's KVM virtualization code for ARM64 processors can leave a freed piece of host memory exposed to a guest virtual machine on hosts with nested virtualization enabled. The bug, tracked as CVE-2026-89775, allows a guest to read and write host kernel memory, and the researcher who found it says it can be used to escape the guest and run code on the host machine.
thehackernews.com
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