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A public disclosure detailed Zapscape, tracked as CVE-2026-64561, a guest-to-host escape vulnerability in KVM/x86 caused by a use-after-free in shadow MMU emulation. The flaw occurs in the recursive shadow-page "zap" path and can be triggered through guest-side actions alone, allowing corruption of host kernel shadow pages and breaking guest-host isolation. The issue affects both Intel and AMD hosts; on Intel, exploitation requires that EPT page walk lengths 4 and 5 are both exposed to the L1 guest, while no equivalent constraint was noted for AMD.
The disclosure warns that systems running untrusted guests with nested virtualization enabled are at particular risk, including multi-tenant x86 public cloud environments. Hyunwoo Kim reported the bug to the Linux kernel security team, and the issue has been patched in mainline Linux. The affected range spans from commit f95eec9bed76 through 2abd5287f083, covering code introduced in 2020 and remaining exposed until the July 2026 fix referenced on kernel.org.
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Hyunwoo Kim publicly disclosed Zapscape, tracked as CVE-2026-64561, on the oss-sec mailing list after the linux-distros embargo expired. The disclosure described a use-after-free in KVM/x86 shadow MMU emulation that can enable guest-to-host escape and noted that mainline Linux had been patched.
A fix for the KVM/x86 guest-to-host escape tracked as CVE-2026-64561 was committed in mainline Linux as commit 2abd5287f083. The disclosure identifies this commit as the patch and as the end of the affected code range.
The affected code range for CVE-2026-64561 begins with commit f95eec9bed76, marking the introduction of the vulnerable KVM/x86 shadow MMU behavior later disclosed as Zapscape.
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A newly disclosed KVM/x86 vulnerability, **CVE-2026-64561** or **Zapscape**, allows a privileged L1 guest to break nested virtualization isolation and achieve guest-to-host escape on Linux systems. The bug is a use-after-free in KVM/x86 shadow MMU emulation tied to the recursive shadow-page zap path and stale-root check ordering during guest-triggered page fault handling, enabling corruption of host kernel shadow pages and potential host code execution. Researcher **Hyunwoo Kim** reported the flaw to the Linux kernel security team and published a proof-of-concept showing creation of a root-owned file on the host. The issue affects both **Intel** and **AMD** hosts and is especially serious for environments that run untrusted guests with nested virtualization enabled, including multi-tenant public cloud infrastructure. On Intel, exploitation requires exposing both EPT page walk lengths 4 and 5 to the L1 guest, while no equivalent constraint was noted for AMD. The vulnerability affects Linux KVM versions from **5.9 onward** across the disclosed commit range, and a fix has been merged upstream into mainline Linux, with users advised to deploy patched stable kernels or vendor-backported updates; no in-the-wild exploitation has been claimed.
Aug 7, 2026
A long-standing flaw in Linux `KVM/x86` shadow paging, tracked as **CVE-2026-53359** and dubbed **Januscape**, can let a guest corrupt host kernel memory and potentially escape isolation. The bug is a use-after-free in KVM shadow MMU emulation caused by incomplete cleanup logic that left stale references to freed page-table tracking structures; reporting indicates earlier validation checked only the guest frame number and not the page role. The issue affects both Intel and AMD hosts, has reportedly existed since Linux kernel `2.6.36`, and was disclosed as a vulnerability that can be triggered solely through guest-side actions.
Jul 12, 2026
A use-after-free vulnerability in KVM's shadow paging code was disclosed after researchers Alexander Bulekov and Fred Griffoul of Amazon found stale reverse mappings in shadow EPT through fuzzing. The flaw affects x86 guests and is exploitable when nested virtualization is enabled on Intel or AMD processors, or when systems use shadow paging with EPT or NPT disabled. Maintainers said the bug can lead to kernel memory corruption and denial of service on the host, making it a guest-to-host risk in affected virtualization setups. The disclosure was coordinated by Sandipan Roy, who said reporters and maintainers agreed to an embargo that ended on March 29, 2026 at 16:00 UTC. Solar Designer said the issue had first been shared with the `linux-distros` list on March 10, 2026 and acknowledged the embargo exceeded that list's usual 14-day limit without prior approval, though it was allowed because the overrun was moderate and multiple stakeholders were already involved. The discussion also noted that on Linux kernels `6.16` and newer, the reproducer hits a `WARN` introduced by commit `11d45175111d`, raising questions about whether `panic_on_warn` could reduce exploitability.
Jun 29, 2026