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

Overview

Severity
Critical (CVSS 9.3)
CVSS Vector
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H/E:U/RL:O/RC:C
Category
Elevation of Privilege
Exploit Status
Not Exploited
Exploitation Likelihood
Less Likely
Patch Tuesday
2026-May
Released
2026-05-12

Description

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

FAQ

What privileges could be gained by an attacker who successfully exploited this vulnerability? An attacker who successfully exploited this vulnerability could gain SYSTEM privileges. Under what circumstances might this vulnerability be exploited other than as a denial of service attack against a Hyper-V host? This issue allows a guest VM to force the Hyper-V host's kernel to read from an arbitrary, potentially invalid address. The contents of the address read would not be returned to the guest VM. In most circumstances, this would result in a denial of service of the Hyper-V host (bugcheck) due to reading an unmapped address. It is possible to read from a memory mapped device register corresponding to a hardware device attached to the Hyper-V host which may trigger additional, hardware device specific side effects that could compromise the Hyper-V host's security. According to the CVSS metric, a successful exploitation could lead to a scope change (S:C). What does this mean for this vulnerability? In this case, a successful attack could be performed from a low privilege Hyper-V guest. The attacker could traverse the guest's security boundary to gain access to the Hyper-V host environment.

Affected Products (4)

Windows

  • Windows Server 2022
  • Windows Server 2022 (Server Core installation)
  • Windows 11 Version 23H2 for ARM64-based Systems
  • Windows 11 Version 23H2 for x64-based Systems

Security Updates (3)

Acknowledgments

<a href="https://x.com/0xashutosh">Ashutosh</a> with <a href="https://www.skyhighsecurity.com/">skyhighsecurity</a>

Revision History

  • 2026-05-12: Information published.