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

Quick assessment

Affected
Linux Linux
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会开源的一款操作系统内核。 Linux kernel 5.9版本存在安全漏洞，该漏洞源于KVM x86在使MMU页面可用后检查无效/过时root，可能导致内存映射到无效根页面，违反活动MMU页面列表不变量。

CVSS 8.8 · High EPSS 0.35% · P27

Affected Version Matrix 16

VendorProduct Version RangeStatus
Linux Linux f95eec9bed76d42194c23153cb1cc8f186bf91cb< 62ef67af1878fa2cd066642f2f59e33ade95f637 affected
f95eec9bed76d42194c23153cb1cc8f186bf91cb< 65c4f7a1028cf01a93a2762d679c289810ede990 affected
f95eec9bed76d42194c23153cb1cc8f186bf91cb< 35e77467610c4a37cb0ff54ee56b85f73b1f5700 affected
f95eec9bed76d42194c23153cb1cc8f186bf91cb< 0026dbb7de8ea76e97d6edf42fc3cc084564e2bf affected
f95eec9bed76d42194c23153cb1cc8f186bf91cb< f3477a6a4164f15287444eda685b5f6405dbd1e5 affected
f95eec9bed76d42194c23153cb1cc8f186bf91cb< bce0d3c26e2c761a4bf43c8949f333fc7374eb2d affected
f95eec9bed76d42194c23153cb1cc8f186bf91cb< 2abd5287f08319fa35764566b15c6e22cb1068db affected
5.9 affected
… +8 more rows
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I. Basic Information for CVE-2026-64561

Vulnerability Information
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Vulnerability Title
KVM: x86: Check for invalid/obsolete root *after* making MMU pages available
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会开源的一款操作系统内核。 Linux kernel 5.9版本存在安全漏洞，该漏洞源于KVM x86在使MMU页面可用后检查无效/过时root，可能导致内存映射到无效根页面，违反活动MMU页面列表不变量。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux f95eec9bed76d42194c23153cb1cc8f186bf91cb ~ 62ef67af1878fa2cd066642f2f59e33ade95f637 -
Linux Linux 5.9 -

II. Public POCs for CVE-2026-64561

# POC Description Source Link Shenlong Link
AI-Generated POC Verified env Premium
Qwen3.6-35B-A3B · 8381 chars
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III. Intelligence Information for CVE-2026-64561

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Patches & Fixes for CVE-2026-64561 (4)

Proof of Concept for CVE-2026-64561 (1)

Other References for CVE-2026-64561 (1)

Same Patch Batch · Linux · 2026-08-04 · 5 CVEs total

CVE-2026-64564 9.8 CRITICAL sctp: don't free the ASCONF's own transport in DEL-IP processing
CVE-2026-64562 8.8 HIGH KVM: nVMX: Hide shadow VMCS right after VMCLEAR
CVE-2026-64563 7.8 HIGH rhashtable: clear stale iter->p on table restart
CVE-2026-64565 Input: ims-pcu - fix heap-buffer-overflow in ims_pcu_process_data()

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-64561

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