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

1. In CISA KEV: not seen
2. Exploited (reported): not seen
3. Scanning observed: not seen
4. Proof of concept public8 public GitHub repositories (unverified), listed by PoC-in-GitHub7 Aug
5. Not established: not seen

DescriptionNVD

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.

Exploitation

Unlikely (under 1%). EPSS under 1%, or no score yet.

CISA KEV

Not listed

Public check

No public nuclei template

Weakness

Race Condition · Race Conditions

Vendor

Linux

Published

August 2026

Band

Unlikely (under 1%), August 2026

1. 7 Aug
   PoC-in-GitHub lists 8 public GitHub repositories (unverified) PoC-in-GitHub

• NVD entrynvd.nist.gov
• Vendor advisorygit.kernel.org
• CVE recordcve.org