CVE-2026-64561 KVM: x86: Check for invalid/obsolete root *after* making MMU pages available

What is CVE-2026-64561?

CVE-2026-64561 is a high-severity vulnerability in Linux, published on 4 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.

Official 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, inheriting role.invalid when creating child shadow pages is also far from ideal; that flaw will be addressed separately.

Weakness: CWE-362

Which versions are affected by CVE-2026-64561?

How do I fix CVE-2026-64561?

Apply the vendor's patch.

Is CVE-2026-64561 being exploited?

There is no known exploitation of CVE-2026-64561 in the wild and no public exploit code.

Public exploit code: 8 proofs of concept on GitHub.

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as AZL-94368, BELL-CVE-2026-64561, DEBIAN-CVE-2026-64561, GHSA-hp26-g45f-hxp5, OESA-2026-3709, UBUNTU-CVE-2026-64561.