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

Critical 9.3 Published 12 May 2026 Updated 10 Aug 2026

A use-after-free flaw in Windows Hyper-V allows local attackers to elevate privileges, requiring immediate patching for Windows 11 and Server 2022 users.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Local or same network only
Victim action needed: Not needed
Fix: None listed

What is CVE-2026-40402?

CVE-2026-40402 is a critical use after free vulnerability in Microsoft Windows 11 23h2, published on 12 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

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

Weakness: CWE-416

Which versions are affected by CVE-2026-40402?

It affects 2 products.

Products include Microsoft Windows 11 23h2, Microsoft Windows Server 2022.

How do I fix CVE-2026-40402?

No fix has been published for CVE-2026-40402 yet. Limit exposure of the affected software until one is available.

Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.

Is CVE-2026-40402 being exploited?

There is no known exploitation of CVE-2026-40402 in the wild and no public exploit code.

All Microsoft Windows 11 23h2 vulnerabilities

Sources

Also known as GHSA-h659-hh52-mv97.