High7.8Microsoft Server Exploited CISA KEV

High [CVE-2021-43226] Windows Common Log File System Driver Elevation of Privilege Vulnerability

This high-severity Microsoft Server advisory covers CVE-2021-43226 affecting Windows Server 2019 (Server Core installation), Windows Server 2022, Windows Server version 2004.

CVE-2021-43226 Published Dec 15, 2021Updated by vendor Aug 22, 2026

CVE-2021-43226

Affected products & platforms

Microsoft ServerWindows Server

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Summary

Windows Common Log File System Driver Elevation of Privilege Vulnerability

Affected products named by the advisory: Windows Server 2019; Windows Server 2019 (Server Core installation); Windows Server 2022; Windows Server version 2004; and 11 more.

Affected products named by the advisory: Windows Server version 20H2; Windows Server 2016 (Server Core installation); Windows Server 2008 Service Pack 2 (Server Core installation); Windows Server 2008 Service Pack 2; and 3 more.

CISA Known Exploited Vulnerability

Listed:: Oct 6, 2025 · federal remediation due Oct 27, 2025
Required action:: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Ransomware use:: Known

KEV is a prioritization signal from CISA — remediation detail still comes from the vendor advisory.

Affected versions

Windows 10 Version 1809 10.0.0 before 10.0.17763.2366
Windows Server 2019 10.0.0 before 10.0.17763.2366
Windows Server 2019 (Server Core installation) 10.0.0 before 10.0.17763.2366
Windows 10 Version 1909 10.0.0 before 10.0.18363.1977
Windows 10 Version 21H1 10.0.0 before 10.0.19043.1415
Windows Server 2022 10.0.0 before 10.0.20348.405
Windows 10 Version 2004 10.0.0 before 10.0.19041.1415
Windows Server version 2004 10.0.0 before 10.0.19041.1415
Windows 10 Version 20H2 10.0.0 before 10.0.19042.1415
Windows Server version 20H2 10.0.0 before 10.0.19042.1415
Windows 11 version 21H2 10.0.0 before 10.0.22000.376
Windows 10 Version 21H2 10.0.0 before 10.0.19044.1415

Official advisory · high-confidence parse· fetched 1 hour ago·verify at source

Fixed versions

10.0.17763.2366
10.0.18363.1977
10.0.19043.1415
10.0.20348.405
10.0.19041.1415
10.0.19042.1415
10.0.22000.376
10.0.19044.1415
10.0.10240.19145
10.0.14393.4825
6.1.7601.25796
6.3.9600.20207

Official advisory · high-confidence parse· fetched 1 hour ago·verify at source

Mitigation

Upgrade to a fixed release: 10.0.17763.2366, 10.0.18363.1977, 10.0.19043.1415, 10.0.20348.405, 10.0.19041.1415, 10.0.19042.1415. That is the remediation for this advisory.

The vendor advisory may list additional interim mitigations or workarounds not captured here — review it before change work.

Official advisory · high-confidence parse· fetched 1 hour ago·verify at source

Discussion(0)

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