CVE-2026-21255: Windows Hyper-V Security Feature Bypass Vulnerability

Overview

Severity

High (CVSS 8.8)

CVSS Vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H/E:U/RL:O/RC:C

Category

Security Feature Bypass

Exploit Status

Not Exploited

Exploitation Likelihood

Less Likely

Patch Tuesday

2026-Feb

Released

2026-02-10

Last Updated

2026-02-10

EPSS Score

0.03% (percentile: 8.9%)

Description

Improper access control in Windows Hyper-V allows an authorized attacker to bypass a security feature locally.

FAQ

What kind of security feature could be bypassed by successfully exploiting this vulnerability? An attacker who successfully exploited this vulnerability could bypass the Virtualization-based Security feature. How could an attacker exploit this vulnerability? Exploitation requires an attacker who already has local execution on a VBS‑enabled guest VM to run a specially crafted application or driver that abuses the hypervisor’s overlay handling to bypass VBS/VTL protections and compromise kernel integrity. According to the CVSS metric, a successful exploitation could lead to a scope change (S:C). What does this mean for this vulnerability? An exploited vulnerability can affect resources beyond the security scope managed by the security authority of the vulnerable component. In this case, the vulnerable component and the impacted component are different and managed by different security authorities.

Affected Products (21)

Windows

• Windows 11 Version 26H1 for ARM64-based Systems
• Windows 11 version 26H1 for x64-based Systems
• Windows 10 Version 1809 for x64-based Systems
• Windows Server 2019
• Windows Server 2019 (Server Core installation)
• Windows Server 2022
• Windows Server 2022 (Server Core installation)
• Windows 10 Version 21H2 for x64-based Systems
• Windows Server 2025 (Server Core installation)
• Windows 11 Version 25H2 for ARM64-based Systems
• Windows 11 Version 25H2 for x64-based Systems
• Windows 11 Version 23H2 for ARM64-based Systems
• Windows 11 Version 23H2 for x64-based Systems
• Windows Server 2022, 23H2 Edition (Server Core installation)
• Windows 11 Version 24H2 for ARM64-based Systems
• Windows 11 Version 24H2 for x64-based Systems
• Windows Server 2025
• Windows 10 Version 1607 for x64-based Systems
• Windows Server 2016
• Windows Server 2016 (Server Core installation)

ESU

• Windows 10 Version 22H2 for x64-based Systems

Security Updates (12)

• 5077179
• 5075904
• 5075906
• 5075943
• 5075912
• 5075899
• 5075942
• 5077181
• 5077212
• 5075941
• 5075897
• 5075999

Acknowledgments

Sai Ganesh Ramachandran with Microsoft

Revision History

• 2026-02-10: Information published.
• 2026-02-10: The FAQs have been updated for this CVE