CVE-2026-40402

Host privilege escalation via use after free

Published May 12, 2026 · Updated May 12, 2026

Use after free in Windows Hyper-V on affected Windows 11 and Windows Server 2022 builds allows local users to gain host privileges. Microsoft identifies Hyper-V as the locus but has not disclosed which object is freed prematurely or which subsequent access reuses it. Reachability is local and unauthenticated, and successful exploitation crosses a security boundary to compromise the host.

CVSS severity9.3
Critical
EPSS probability0.33%
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 Windows Hyper-V on affected Windows 11 and Windows Server 2022 builds allows local users to gain host privileges. Microsoft identifies Hyper-V as the locus but has not disclosed which object is freed prematurely or which subsequent access reuses it. Reachability is local and unauthenticated, and successful exploitation crosses a security boundary to compromise the host.

The record

CVE
CVE-2026-40402
Published
May 12, 2026
Updated
May 12, 2026
Vendor
Microsoft
Product
Windows 11 Version 22H3
Classifications
CWE-416, T1068
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 12, 2026CVE publishedPublication date reported by the CVE source.
  2. May 12, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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

  1. Affected versionversion=10.0.22631.0 <10.0.22631.7079

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Microsoft · Windows 11 Version 22H3version=10.0.22631.0 <10.0.22631.7079
Microsoft · Windows 11 Version 23H2version=10.0.22631.0 <10.0.22631.7079
Microsoft · Windows Server 2022version=10.0.20348.0 <10.0.20348.5139

Published CVSS scores

9.3MicrosoftCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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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