What is CVE-2026-40402?

CVE-2026-40402 is a critical-severity vulnerability in Microsoft Windows_11_23h2, classified under Use After Free. CVSS score: 9.3/10. Published 2026-05-12.

How severe is CVE-2026-40402?

Critical severity. CVSS v3 base score is 9.3 out of 10.

Use After Free in Microsoft Windows_11_23h2

CVE-2026-40402

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

Vulnerability class: Use-After-Free

EPSS: 0.001 (18.1th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 9.3 (Critical). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H.

Affected products

Microsoft Windows_11_23h2
Microsoft Windows 11 Version 22h3 — versions 10.0.22631.0
Microsoft Windows 11 Version 23h2 — versions 10.0.22631.0
Microsoft Windows Server 2022 — versions 10.0.20348.0
Microsoft Windows_server_2022

Weakness classification (CWE)

CWE-416 — Use After Free

References

Windows Hyper-V Elevation of Privilege Vulnerability (vendor-advisory, patch, Vendor Advisory)

Frequently asked questions

What is CVE-2026-40402?: CVE-2026-40402 is a critical-severity vulnerability in Microsoft Windows_11_23h2, classified under Use After Free. CVSS score: 9.3/10. Published 2026-05-12.
How severe is CVE-2026-40402?: Critical severity. CVSS v3 base score is 9.3 out of 10.