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Zapscape
Zapscape is a root-validation ordering flaw in the Linux kernel's x86 KVM shadow MMU page-fault handling. KVM checks whether a shadow page-table root is invalid or obsolete before making shadow MMU pages available. Reclaiming shadow pages during that operation can invalidate an in-use root, after which KVM may attempt to populate it. Newly created child shadow pages inherit the parent's invalid role and can enter the active MMU-page list, violating the invariant that invalid pages must never appear on that list. The underlying root-tracking flaw dates to 2008; the active-page invariant introduced in Linux 5.9 made the flaw problematic. The resulting inconsistent MMU state can destabilize affected virtualization workloads and potentially compromise the virtualization security boundary.
What it means and what to do now: patch path, interim mitigations, and the assume-compromise checklist.
What an attacker gets, and what they’ve been doing with it.
Exploitation can corrupt KVM shadow-MMU state, potentially causing kernel instability or denial of service affecting virtualization workloads. The vulnerability-specific security assessment also identifies potential high confidentiality, integrity, and availability impacts across a changed security scope. A specific arbitrary-code-execution or guest-escape mechanism is not established by the available technical details.
If you can’t patch tonight, do this now.
Until updates are deployed, restrict untrusted local access to virtualization hosts and limit which users or workloads can create or control KVM virtual machines. Isolate untrusted virtualization workloads and reduce use of the affected x86 KVM shadow-MMU path where operationally feasible. These measures reduce exposure but do not correct the root-validation flaw.
Patch, then assume compromise.
Install a supported kernel update containing the KVM x86 fix that checks for invalid or obsolete roots after making shadow MMU pages available. Reboot into the fixed kernel unless an applicable supported live patch is deployed. SUSE provides kernel and live-patch updates for affected product streams. Listed Debian fixes include linux 6.12.101-1 for trixie and linux-6.12 6.12.101-1~deb12u1 for bookworm. Google Container-Optimized OS fixed versions include 18867.528.65 for COS 121, 19216.532.108 for COS 125, and 19506.299.137 for COS 129, or later supported builds in the corresponding stream. Verify that the running kernel includes the fix rather than relying solely on installed-package status.
1 exploit validated by Mallory's analysis. Hidden: 7 rejected by Mallory's analysis as not a working exploit.
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
138 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.