CVEs / CVE-2021-43226
CVE-2021-43226: Microsoft Windows Privilege Escalation Vulnerability
- Known exploited in the CISA KEV catalog since 6 Oct 2025
- high 7.8 CVSS 3.1 (NVD)
- EPSS 3.27% chance of exploitation in the next 30 days, higher than 88% of CVEs (30 Oct 2026)
- Last changed at its sources
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Summary
Microsoft Windows Common Log File System Driver contains a privilege escalation vulnerability that could allow a local, privileged attacker to bypass certain security mechanisms.
Description
Windows Common Log File System Driver Elevation of Privilege Vulnerability
Affected and fixed versions
| Product | Affected | Fixed in |
|---|---|---|
| Microsoft Windows 10 Version 1809 | from 10.0.0, before 10.0.17763.2366 | 10.0.17763.2366 |
| Microsoft Windows Server 2019 | from 10.0.0, before 10.0.17763.2366 | 10.0.17763.2366 |
| Microsoft Windows Server 2019 (Server Core installation) | from 10.0.0, before 10.0.17763.2366 | 10.0.17763.2366 |
| Microsoft Windows 10 Version 1909 | from 10.0.0, before 10.0.18363.1977 | 10.0.18363.1977 |
| Microsoft Windows 10 Version 21H1 | from 10.0.0, before 10.0.19043.1415 | 10.0.19043.1415 |
| Microsoft Windows Server 2022 | from 10.0.0, before 10.0.20348.405 | 10.0.20348.405 |
| Microsoft Windows 10 Version 2004 | from 10.0.0, before 10.0.19041.1415 | 10.0.19041.1415 |
| Microsoft Windows Server version 2004 | from 10.0.0, before 10.0.19041.1415 | 10.0.19041.1415 |
| Microsoft Windows 10 Version 20H2 | from 10.0.0, before 10.0.19042.1415 | 10.0.19042.1415 |
| Microsoft Windows Server version 20H2 | from 10.0.0, before 10.0.19042.1415 | 10.0.19042.1415 |
| Microsoft Windows 11 version 21H2 | from 10.0.0, before 10.0.22000.376 | 10.0.22000.376 |
| Microsoft Windows 10 Version 21H2 | from 10.0.0, before 10.0.19044.1415 | 10.0.19044.1415 |
| Microsoft Windows 10 Version 1507 | from 10.0.0, before 10.0.10240.19145 | 10.0.10240.19145 |
| Microsoft Windows 10 Version 1607 | from 10.0.0, before 10.0.14393.4825 | 10.0.14393.4825 |
| Microsoft Windows Server 2016 | from 10.0.0, before 10.0.14393.4825 | 10.0.14393.4825 |
| Microsoft Windows Server 2016 (Server Core installation) | from 10.0.0, before 10.0.14393.4825 | 10.0.14393.4825 |
| Microsoft Windows 7 | from 6.1.0, before 6.1.7601.25796 | 6.1.7601.25796 |
| Microsoft Windows 7 Service Pack 1 | from 6.1.0, before 6.1.7601.25796 | 6.1.7601.25796 |
| Microsoft Windows 8.1 | from 6.3.0, before 6.3.9600.20207 | 6.3.9600.20207 |
| Microsoft Windows Server 2008 Service Pack 2 | from 6.0.0, before 6.0.6003.21309 | 6.0.6003.21309 |
| Microsoft Windows Server 2008 Service Pack 2 (Server Core installation) | from 6.0.0, before 6.0.6003.21309 | 6.0.6003.21309 |
| Microsoft Windows Server 2008 Service Pack 2 | from 6.0.0, before 6.0.6003.21309 | 6.0.6003.21309 |
| Microsoft Windows Server 2008 R2 Service Pack 1 | from 6.1.0, before 6.1.7601.25796 | 6.1.7601.25796 |
| Microsoft Windows Server 2008 R2 Service Pack 1 (Server Core installation) | from 6.0.0, before 6.1.7601.25796 | 6.1.7601.25796 |
| Microsoft Windows Server 2012 | from 6.2.0, before 6.2.9200.23545 | 6.2.9200.23545 |
| Microsoft Windows Server 2012 | from 6.2.0, before 6.2.9200.23540 | 6.2.9200.23540 |
| Microsoft Windows Server 2012 (Server Core installation) | from 6.2.0, before 6.2.9200.23545 | 6.2.9200.23545 |
| Microsoft Windows Server 2012 (Server Core installation) | from 6.2.0, before 6.2.9200.23540 | 6.2.9200.23540 |
| Microsoft Windows Server 2012 R2 | from 6.3.0, before 6.3.9600.20207 | 6.3.9600.20207 |
| Microsoft Windows Server 2012 R2 (Server Core installation) | from 6.3.0, before 6.3.9600.20207 | 6.3.9600.20207 |
Exploitation
| In CISA KEV since | 6 Oct 2025 |
|---|---|
| Due date for US federal agencies | 27 Oct 2025 |
| Used in ransomware campaigns | Known |
| 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. |
Severity
| CVSS 3.1 | 7.8 highCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HScored by NVD |
|---|
References
- CVE-2021-43226 on NVD
- CVE-2021-43226 in the CISA KEV catalog
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-43226 (cited by CISA)
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-43226 Patch, Vendor Advisory
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-43226 US Government Resource
Sources
Exploitation status from the CISA Known Exploited Vulnerabilities catalog. EPSS scores from FIRST. Descriptions, severity and references from the National Vulnerability Database. Open-source package versions from OSV (CC-BY 4.0). Text is shown as each source states it; Stackurity does not edit it. Check the vendor's advisory before acting.
This product uses data from the NVD API but is not endorsed or certified by the NVD.