Linux KVM/arm64 Vulnerability Lets Attackers Escape Virtual Machines and Gain Host Access
CVE-2026-89775 lets a malicious ARM64 KVM guest skip TLB invalidation and access host memory.
Hyunwoo Kim disclosed CVE-2026-89775, a Linux KVM/arm64 flaw in stage-1 page-table walks when nested virtualization is enabled. A size calculation can return 0, which VNCR pseudo-TLB logic treats as valid, skipping invalidation and leaving a freed host page writable at a fixed kernel address. A malicious guest can then read and write that page without a VM exit, breaking cloud isolation or, where /dev/kvm is mode 0666, escalating locally to root. The code was introduced on May 14, 2025 and fixed upstream on August 6, 2026 by commit 8053393680d4.
- CVE-2026-89775 is a type-truncation bug in KVM/arm64 stage-1 page-table walks.
- A zero size skips VNCR pseudo-TLB invalidation, leaving stale writable host mappings.
- Nested virtualization can give a guest 64-bit access to a freed host page.
- Code landed May 14, 2025 and was fixed upstream on August 6, 2026.
- World-writable /dev/kvm on some systems may enable local root.
- CVEs
- CVE-2026-89775
- Vendors
- Linux
- Products
- Linux kernelKVM
- Organizations
- Red Hat
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
2 min read at cybersecuritynews.com
A newly disclosed Linux kernel vulnerability, tracked as CVE-2026-89775, could let attackers escape an ARM64 virtual machine and access the underlying host system. The issue affects KVM/arm64 environments where nested virtualization is enabled, creating a serious risk for multi-tenant cloud infrastructure and systems that allow untrusted users to create virtual machines. Security researcher Hyunwoo Kim […]
By Abinaya · cybersecuritynews.com
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