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

CVE-2026-40402 is fixed in 4 products on 1 platform, first by KB5087420, released May 12, 2026. It is not reported as exploited. Patch Radar priority: Urgent.

- Web page: https://patchblox.com/security/cve/CVE-2026-40402
- Priority: Urgent
- CVSS: 9.3 (Critical)
- EPSS: 0.0033
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Vendor exploitability assessment: Exploitation Less Likely
- Published: May 12, 2026
- Weakness: Use After Free
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40402

## Description

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

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Microsoft | Windows 11 Version 23H2 for ARM64-based Systems | 22631.7079 | [KB5087420](https://patchblox.com/security/data/fix/microsoft/kb5087420.md) | May 12, 2026 |
| Microsoft | Windows 11 Version 23H2 for x64-based Systems | 22631.7219 | [KB5093998](https://patchblox.com/security/data/fix/microsoft/kb5093998.md) | Jun 9, 2026 |
| Microsoft | Windows Server 2022 | 20348.5074 | [KB5087424](https://patchblox.com/security/data/fix/microsoft/kb5087424.md) | May 12, 2026 |
| Microsoft | Windows Server 2022 | 20348.5139 | [KB5087545](https://patchblox.com/security/data/fix/microsoft/kb5087545.md) | May 12, 2026 |
| Microsoft | Windows Server 2022 (Server Core installation) | 20348.5074 | [KB5087424](https://patchblox.com/security/data/fix/microsoft/kb5087424.md) | May 12, 2026 |
| Microsoft | Windows Server 2022 (Server Core installation) | 20348.5139 | [KB5087545](https://patchblox.com/security/data/fix/microsoft/kb5087545.md) | May 12, 2026 |

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Data as of 2026-11-08T06:59:42Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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