Is CVE-2021-43226 being actively exploited?

Yes. CVE-2021-43226 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, added on October 6, 2025.

What is the CVSS score for CVE-2021-43226?

CVE-2021-43226 has a CVSS 3.1 base score of 7.8 (HIGH).

CVE-2021-43226

HIGH · CVSS 7.8CISA KEV: actively exploitedEPSS 3.3%EU EUVD: exploited

Windows Common Log File System Driver Elevation of Privilege Vulnerability

Key facts

CVSS score: 7.8 (v3.1)
Severity: HIGH
CVSS vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS score: 3.3% (88th percentile)
In CISA KEV: Yes, added October 6, 2025
In EU EUVD: Yes (EUVD-2021-30170)
Published: December 15, 2021
NVD last modified: August 22, 2026
Status: Analyzed

CISA Known Exploited Vulnerability

Microsoft Windows Privilege Escalation Vulnerability

Added to the KEV catalog on October 6, 2025; federal remediation due October 27, 2025. Known to be used in ransomware campaigns.

EU Vulnerability Database (EUVD)

This vulnerability is also tracked by ENISA as EUVD-2021-30170 in the EU Vulnerability Database. ENISA flags it as known exploited. Last updated in EUVD on August 22, 2026.

View on the EU Vulnerability Database

Affected products

microsoft / windows 10 1507
microsoft / windows 10 1507
microsoft / windows 10 1607
microsoft / windows 10 1607
microsoft / windows 10 1809
microsoft / windows 10 1909
microsoft / windows 10 2004
microsoft / windows 10 20h2
microsoft / windows 10 20h2
microsoft / windows 10 21h1
microsoft / windows 10 21h2
microsoft / windows 11 21h2
microsoft / windows 7
microsoft / windows 8.1
microsoft / windows rt 8.1
microsoft / windows server 2004
microsoft / windows server 2008
microsoft / windows server 2008
microsoft / windows server 2008
microsoft / windows server 2012
microsoft / windows server 2012
microsoft / windows server 2016
microsoft / windows server 2019
microsoft / windows server 2022
microsoft / windows server 20h2

Certified products that may be affected

4 FIPS 140 or Common Criteria certified products, from automated matching by sec-certs.org.

Microsoft Windows 10 version 2004 (May 2020 Update), Microsoft Windows Server version 2004 (May 2020 Update) and others - Microsoft Corporation - Common Criteria 2020-50-INF-3671 - active
Microsoft Windows 10 version 1909 and Microsoft Windows Server version 1909 - Microsoft Corporation - Common Criteria 2019-47-INF-3134 - archived
Windows 7 BitLocker™ Drive Encryption - Microsoft Corporation - FIPS 140 1332 - historical
Microsoft Windows 7 Kernel Mode Cryptographic Primitives Library (cng.sys) - Microsoft Corporation - FIPS 140 1328 - historical

References

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)

Last updated September 17, 2026 · Source: NVD, CISA KEV, FIRST.org EPSS

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