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CVE-2021-43226: Microsoft Windows Privilege Escalation Vulnerability

• Severity: high (CVSS 7.8 v3.1)
• Exploited in the wild: yes — in CISA KEV since 2025-10-06
• EPSS: 3.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-12-15 · updated 2026-08-22

Description

Windows Common Log File System Driver Elevation of Privilege Vulnerability

Affected products

• Microsoft Windows 10 Version 1507: before 10.0.10240.19145 — fixed in 10.0.10240.19145
• Microsoft Windows 10 1607: before 10.0.14393.4825 — fixed in 10.0.14393.4825
• Microsoft Windows 10: before 10.0.17763.2366 — fixed in 10.0.17763.2366
• Microsoft Windows 10 1909: before 10.0.18363.1977 — fixed in 10.0.18363.1977
• Microsoft Windows 10 2004: before 10.0.19041.1415 — fixed in 10.0.19041.1415
• Microsoft Windows 10 20H2: before 10.0.19042.1415 — fixed in 10.0.19042.1415
• Microsoft Windows 10 21H1: before 10.0.19043.1415 — fixed in 10.0.19043.1415
• Microsoft Windows 10: before 10.0.19044.1415 — fixed in 10.0.19044.1415
• Microsoft Windows 11 21H2: before 10.0.22000.376 — fixed in 10.0.22000.376
• Microsoft Windows 7: all versions
• Microsoft Windows 8.1: all versions
• Microsoft Windows RT 8.1: all versions
• Microsoft Windows Server 2004: before 10.0.19041.1415 — fixed in 10.0.19041.1415
• Microsoft Windows Server 2008: r2-sp1
• Microsoft Windows Server 2012: r2
• Microsoft Windows Server 2016: before 10.0.14393.4825 — fixed in 10.0.14393.4825
• Microsoft Windows Server 2019: before 10.0.17763.2366 — fixed in 10.0.17763.2366
• Microsoft Windows Server 2022: before 10.0.20348.405 — fixed in 10.0.20348.405
• Microsoft Windows Server 20H2: before 10.0.19042.1415 — fixed in 10.0.19042.1415

How to fix

Upgrade to a fixed version: Microsoft Windows 10 Version 1507 10.0.10240.19145; Microsoft Windows 10 1607 10.0.14393.4825; Microsoft Windows 10 10.0.17763.2366; Microsoft Windows 10 1909 10.0.18363.1977; Microsoft Windows 10 2004 10.0.19041.1415; Microsoft Windows 10 20H2 10.0.19042.1415; Microsoft Windows 10 21H1 10.0.19043.1415; Microsoft Windows 10 10.0.19044.1415; Microsoft Windows 11 21H2 10.0.22000.376; Microsoft Windows Server 2004 10.0.19041.1415; Microsoft Windows Server 2016 10.0.14393.4825; Microsoft Windows Server 2019 10.0.17763.2366. Check the vendor advisory for mitigations.

References

• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-43226
• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-43226
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-43226

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