CVE-2026-23401

Host privilege escalation via stale shadow SPTE

Published Apr 1, 2026 · Updated Apr 1, 2026

Use-after-free in the KVM x86 MMU allows local users to escalate privileges or crash the Linux host through a guest page fault. When host userspace changes a shadowed guest page-table entry from a memory slot to emulated MMIO, mmu_set_spte installs an MMIO SPTE without first zapping the existing present SPTE. Triggering the related guest page fault reaches the stale entry; exploitation requires local KVM access and an x86 host using the affected MMU path.

CVSS severity5.5
Medium
EPSS probability0.18%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in the KVM x86 MMU allows local users to escalate privileges or crash the Linux host through a guest page fault. When host userspace changes a shadowed guest page-table entry from a memory slot to emulated MMIO, mmu_set_spte installs an MMIO SPTE without first zapping the existing present SPTE. Triggering the related guest page fault reaches the stale entry; exploitation requires local KVM access and an x86 host using the affected MMU path.

The record

CVE
CVE-2026-23401
Published
Apr 1, 2026
Updated
Apr 1, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-416, T1068
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 1, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 1, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=5.13
  2. Affected versionversion=a54aa15c6bda3ca7e2f9e040ba968a1da303e24f <aad885e774966e97b675dfe928da164214a71605

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=5.13; version=a54aa15c6bda3ca7e2f9e040ba968a1da303e24f <aad885e774966e97b675dfe928da164214a71605

Published CVSS scores

5.5Canonical UbuntuCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
5.5Amazon LinuxCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
8.1Red Hat Product SecurityCVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
8.8Oracle LinuxCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
6.5SUSECVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-416Use After Free
T1068Exploitation for Privilege Escalation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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