CVE-2026-64561

Technical Description

In the Linux kernel, the following vulnerability has been resolved:

KVM: x86: Check for invalid/obsolete root *after* making MMU pages available

Check for a "stale" page fault, i.e. for an invalid and/or obsolete root,

after making MMU pages available for the shadow MMU. If reclaiming shadow

pages zaps an in-use root, i.e. marks it invalid, then KVM will attempt to

map memory into an invalid root. On its own, populating an invalid root is

"fine", but because child shadow pages inherit their parent's role, any

children created during the map/fetch will be created as invalid pages,

thus violating KVM's invariant that invalid pages are never on the list of

active MMU pages.

Note, the underlying flaw has existed since KVM first started tracking

invalid roots in 2008 (commit 2e53d63acba7, "KVM: MMU: ignore zapped root

pagetables"), but the true badness only came along in 2020 (Linux 5.9)

with the invariant that invalid shadow pages can't be on the list of

active pages.

Note #2, inheri

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References