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Vulnerabilities

Vulnerability · CVE-2021-43226

Microsoft Windows Privilege Escalation Vulnerability

Published Dec 15, 2021 · catalog updated Aug 21, 2026 · Microsoft Windows

Patch now

CVE-2021-43226 is in the CISA known-exploited catalog, due Oct 27, 2025. Confirm Microsoft Windows against the vendor advisory and apply that fix. The CVSS score does not change the priority.

Gaps on this record

  • No version range is stored. A customer cannot check an installed version against this record.
Severity
High7.8
Known exploitation
CISA KEV and VulnCheck KEV
EPSS
3.28%
Remediation
Remediation guidance
Affected products
cpe microsoft/windows 10 1507 · cpe microsoft/windows 10 1607 · cpe microsoft/windows 10 1809 · cpe microsoft/windows 10 1909 · cpe microsoft/windows 10 2004 · cpe microsoft/windows 10 20h2

Microsoft Windows Common Log File System Driver contains a privilege escalation vulnerability that could allow a local, privileged attacker to bypass certain security mechanisms.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe microsoft/windows 10 1507version unspecified
  • cpe microsoft/windows 10 1607version unspecified
  • cpe microsoft/windows 10 1809version unspecified
  • cpe microsoft/windows 10 1909version unspecified
  • cpe microsoft/windows 10 2004version unspecified
  • cpe microsoft/windows 10 20h2version unspecified
  • vendor Microsoft Windowsversion unspecified

How to fix CVE-2021-43226

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

CVE-2021-43226 is in the CISA known-exploited catalog, due Oct 27, 2025. Confirm Microsoft Windows against the vendor advisory and apply that fix. The CVSS score does not change the priority.

Which versions are affected?

Affected version ranges are not on this record. Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

What should an analyst verify?

No weakness class is stored. EPSS 3.28%. The CISA KEV listing is the exploitation evidence. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Technology hubs

Windows security

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Dec 15, 2021 · Catalog

    Detected

    Microsoft Windows Common Log File System Driver contains a privilege escalation vulnerability that could allow a local, privileged attacker to bypass certain security mechanisms.

  2. Oct 6, 2025 · CISA KEV

    Known exploited

    Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

  3. Oct 27, 2025 · CISA KEV

    Remediation due

    Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

  4. Aug 21, 2026 · Catalog

    Updated

    Microsoft Windows Common Log File System Driver contains a privilege escalation vulnerability that could allow a local, privileged attacker to bypass certain security mechanisms.

Sources

  • CISA KEVConfirmed exploitationCVE-2021-43226

    Microsoft Windows Common Log File System Driver contains a privilege escalation vulnerability that could allow a local, privileged attacker to bypass certain security mechanisms.

    cisa.gov
  • CVE.orgVulnerability recordCVE-2021-43226

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2021-43226

    30-day exploitation probability 3.3%

    first.org
  • NIST NVDVulnerability recordCVE-2021-43226

    Windows Common Log File System Driver Elevation of Privilege Vulnerability

    nvd.nist.gov
  • VulnCheck KEVConfirmed exploitationCVE-2021-43226

    Microsoft Windows Common Log File System Driver contains a privilege escalation vulnerability that could allow a local, privileged attacker to bypass certain security mechanisms.

    vulncheck.com

References

Freshness

Last verified in this catalog Oct 17, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.