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

mediumpublic exploitCVSS 5.5CVE-2026-64561

CSIRTS triage

vendor: Linuxproduct: KVMPrivilege escalation
What
KVM x86 fails to properly validate invalid/obsolete root states after making MMU pages available, allowing privilege escalation.
Who is affected
Systems running KVM with x86 virtual machines, particularly those with untrusted guest code.
Urgency
Medium priority; local privilege escalation in guest context requires prior guest access.
Action
Update the Linux kernel to incorporate the fix for invalid MMU root validation.

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Details

Source
Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity
medium — CVSS 5.5
Published
2026-08-11
Exploitation
Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-64561

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Referenced CVEs

CVECSIRTS overviewExternal
CVE-2026-64561coverage & exploitation statusNVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

Recent advisories for KVM

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

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