CVE-2026-40402: Windows Hyper-V Elevation of Privilege Vulnerability

Severity: critical (CVSS 9.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-05-12 · updated 2026-08-10
Weakness: CWE-416

Description

Use after free in Windows Hyper-V allows an unauthorized attacker to elevate privileges locally.

Affected products

Microsoft Windows 11: before 10.0.22631.7079 — fixed in 10.0.22631.7079
Microsoft Windows Server 2022: before 10.0.20348.5074 — fixed in 10.0.20348.5074
Microsoft Windows 11: from 10.0.22631.0 before 10.0.22631.7079 — fixed in 10.0.22631.7079
Microsoft Windows Server 2022: from 10.0.20348.0 before 10.0.20348.5139 — fixed in 10.0.20348.5139

How to fix

Upgrade to a fixed version: Microsoft Windows 11 10.0.22631.7079; Microsoft Windows Server 2022 10.0.20348.5074; Microsoft Windows 11 10.0.22631.7079; Microsoft Windows Server 2022 10.0.20348.5139. Check the vendor advisory for mitigations.

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40402

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