CVE-2026-21255

HighCVSS 8.8/10Last modified Jun 17, 2026

Description

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

Metrics

CVSS 3.1 8.8/10CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

Weakness enumeration

CWE-284

Affected software

VendorProductVersions
MicrosoftWindows 10 Version 1607>= 10.0.14393.0, < 10.0.14393.8868
MicrosoftWindows 10 Version 1809>= 10.0.17763.0, < 10.0.17763.8389
MicrosoftWindows 10 Version 21H2>= 10.0.19044.0, < 10.0.19044.6937
MicrosoftWindows 10 Version 22H2>= 10.0.19045.0, < 10.0.19045.6937
MicrosoftWindows 11 version 22H3>= 10.0.22631.0, < 10.0.22631.6649
MicrosoftWindows 11 Version 23H2>= 10.0.22631.0, < 10.0.22631.6649
MicrosoftWindows 11 Version 24H2>= 10.0.26100.0, < 10.0.26100.7840
MicrosoftWindows 11 Version 25H2>= 10.0.26200.0, < 10.0.26200.7840
MicrosoftWindows 11 version 26H1>= 10.0.28000.0, < 10.0.28000.1575
MicrosoftWindows 11 Version 26H1>= 10.0.28000.0, < 10.0.28000.1575
MicrosoftWindows Server 2016>= 10.0.14393.0, < 10.0.14393.8868
MicrosoftWindows Server 2016 (Server Core installation)>= 10.0.14393.0, < 10.0.14393.8868
MicrosoftWindows Server 2019>= 10.0.17763.0, < 10.0.17763.8389
MicrosoftWindows Server 2019 (Server Core installation)>= 10.0.17763.0, < 10.0.17763.8389
MicrosoftWindows Server 2022>= 10.0.20348.0, < 10.0.20348.4773
MicrosoftWindows Server 2022, 23H2 Edition (Server Core installation)>= 10.0.25398.0, < 10.0.25398.2149
MicrosoftWindows Server 2025>= 10.0.26100.0, < 10.0.26100.32370
MicrosoftWindows Server 2025 (Server Core installation)>= 10.0.26100.0, < 10.0.26100.32370

References

Timeline

Published
Feb 10, 2026
Last modified
Jun 17, 2026
NVD status
Analyzed

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CVE-2026-21255: High severity, CVSS 8.8 | Vulnix