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CVE-2021-26867: Windows Hyper-V Remote Code Execution Vulnerability

• Severity: high (CVSS 7.2 v2.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 2.9% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-03-11 · updated 2026-08-19

Description

Windows Hyper-V Remote Code Execution Vulnerability

Affected products

• Microsoft Windows 10 Version 1607: 20h2, 1909, 2004
• Microsoft Windows Server 2016: 20h2, 1909, 2004
• Microsoft Windows 10 1909: from 10.0.0 before 10.0.18363.1440 — fixed in 10.0.18363.1440
• Microsoft Windows 10 2004: from 10.0.0 before 10.0.19043.867 — fixed in 10.0.19043.867
• Microsoft Windows Server, version 1909 (Server Core installation): from 10.0.0 before 10.0.18363.1440 — fixed in 10.0.18363.1440
• Microsoft Windows Server version 2004: from 10.0.0 before 10.0.19043.867 — fixed in 10.0.19043.867
• Microsoft Windows Server version 20H2: from 10.0.0 before 10.0.19043.867 — fixed in 10.0.19043.867

How to fix

Upgrade to a fixed version: Microsoft Windows 10 1909 10.0.18363.1440; Microsoft Windows 10 2004 10.0.19043.867; Microsoft Windows Server, version 1909 (Server Core installation) 10.0.18363.1440; Microsoft Windows Server version 2004 10.0.19043.867; Microsoft Windows Server version 20H2 10.0.19043.867. Check the vendor advisory for mitigations.

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-26867
• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26867

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