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VulnerabilityCVE-2026-64561Published 2026-08-04

CVE-2026-64561 — Linux

highPublic exploit9 PoC repos

As of 2026-08-27, CVE-2026-64561 is a HIGH-severity vulnerability in Linux, CVSS v3.1 8.8, EPSS 0.3% (26.2th percentile). Threadlinqs Intelligence links 1 tracked threat campaign to CVE-2026-64561, most recently “CVE-2026-64561 — Zapscape: KVM/x86 Shadow MMU Use-After-Free Allows L1 Guest Escape to Linux Host”.

CVSS v3.1
8.8/10High
EPSS
0.3%Higher than 26.2% of scored CVEs
CISA KEV
NoNot in the KEV catalog
Tracked threats
1Campaigns referencing it
Priority
7.4/10Threadlinqs triage score
Published
Updated 2026-08-27
CVSS v3.1 8.8 (HIGH) · EPSS 0.3% (higher than 26.2% of all scored CVEs) · Priority 7.4/10 · Published 2026-08-04

Last updated:

What is CVE-2026-64561?

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.

Its CVSS v3 base vector states that the flaw requires local access to the host, needs low-privilege credentials, needs no user interaction, and has high impact on confidentiality, integrity, availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 84 days ago.

Severity and exploitation probability

CVSS v3.1 base score
8.8 — HIGH
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
EPSS (FIRST)
0.3% probability of exploitation in the next 30 days, higher than 26.2% of all scored CVEs
CISA KEV
Not listed in the CISA Known Exploited Vulnerabilities catalog
Threadlinqs priority
7.4/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
Published
2026-08-04, last modified 2026-08-27

Is CVE-2026-64561 being exploited?

Weaponised exploit code for CVE-2026-64561 is publicly available. 9 public proof-of-concept repositories are tracked for this identifier. It currently carries a trending score of 33 in the Threadlinqs vulnerability feed.

Affected products and versions

How to fix CVE-2026-64561

No vendor patch reference has been recorded for CVE-2026-64561 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

Threat activity tracking CVE-2026-64561

1 tracked threat in the Threadlinqs corpus references CVE-2026-64561, either in the campaign’s CVE list or as an indicator on the campaign record.

Sources

Enriched from CVE.org, FIRST EPSS, GitHub Security Advisories, public proof-of-concept repositories. Last verified by Threadlinqs on .

Other references

Showing 5 of 8 recorded references.