Windows CVE-2026-21255
HIGHCVSS VectorNVD
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Lifecycle Timeline
2DescriptionNVD
Improper access control in Windows Hyper-V allows an authorized attacker to bypass a security feature locally.
AnalysisAI
Windows Hyper-V fails to properly enforce access controls, enabling local authenticated users to circumvent security features and gain unauthorized system access. This high-severity flaw affects Windows 10, Windows 11, Windows Server 2022, and Hyper-V implementations, allowing privileged attackers to escalate privileges across system boundaries. …
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RemediationAI
Within 24 hours: Inventory all Windows Hyper-V deployments and identify systems with direct user access; restrict administrative privileges to essential personnel only. Within 7 days: Implement network segmentation to isolate Hyper-V hosts from untrusted networks and implement enhanced monitoring for suspicious hypervisor activity. …
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