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CVE-2021-43226

Windows Common Log File System Driver Elevation of Privilege Vulnerability

  • High 7.8
  • Exploited: added to CISA KEV 6 Oct 2025
  • Used in ransomware campaigns

Description

Windows Common Log File System Driver Elevation of Privilege Vulnerability

Key facts

Published
15 Dec 2021
Last changed
22 Aug 2026
Assigned by
microsoft
KEV added
6 Oct 2025
KEV fix due
27 Oct 2025
Used in ransomware
Yes, according to CISA
EPSS
3.275% likely to be exploited in the next 30 days, higher than 88.627% of CVEs (scores for 15 Nov 2026)
SSVC (CISA)
Exploitation: active; Automatable: no; Technical impact: total

Severity scores

Each score is shown as its source gave it. They are not averaged or merged.

  • 7.8CVSS 3.1, Highfrom the CNA (microsoft)CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C

What to do

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

Historical context and remediation

This reference retains the original CVE publication date. A recent record update does not mean a new attack occurred.

No separately sourced impact summary is available on this page yet. Consult the description, version data and dated exploitation evidence.

Version statuses below come from the CNA. An “unaffected” version is not necessarily a currently supported release or proof of a patch date. EPSS is a dated risk estimate, not a count of historical attacks.

Read the original CVE record.

Affected products

VendorProductVersions
MicrosoftWindows 10 Version 1809
  • 10.0.0 up to but excluding 10.0.17763.2366 (affected)
MicrosoftWindows Server 2019
  • 10.0.0 up to but excluding 10.0.17763.2366 (affected)
MicrosoftWindows Server 2019 (Server Core installation)
  • 10.0.0 up to but excluding 10.0.17763.2366 (affected)
MicrosoftWindows 10 Version 1909
  • 10.0.0 up to but excluding 10.0.18363.1977 (affected)
MicrosoftWindows 10 Version 21H1
  • 10.0.0 up to but excluding 10.0.19043.1415 (affected)
MicrosoftWindows Server 2022
  • 10.0.0 up to but excluding 10.0.20348.405 (affected)
MicrosoftWindows 10 Version 2004
  • 10.0.0 up to but excluding 10.0.19041.1415 (affected)
MicrosoftWindows Server version 2004
  • 10.0.0 up to but excluding 10.0.19041.1415 (affected)
MicrosoftWindows 10 Version 20H2
  • 10.0.0 up to but excluding 10.0.19042.1415 (affected)
MicrosoftWindows Server version 20H2
  • 10.0.0 up to but excluding 10.0.19042.1415 (affected)
MicrosoftWindows 11 version 21H2
  • 10.0.0 up to but excluding 10.0.22000.376 (affected)
MicrosoftWindows 10 Version 21H2
  • 10.0.0 up to but excluding 10.0.19044.1415 (affected)
MicrosoftWindows 10 Version 1507
  • 10.0.0 up to but excluding 10.0.10240.19145 (affected)
MicrosoftWindows 10 Version 1607
  • 10.0.0 up to but excluding 10.0.14393.4825 (affected)
MicrosoftWindows Server 2016
  • 10.0.0 up to but excluding 10.0.14393.4825 (affected)
MicrosoftWindows Server 2016 (Server Core installation)
  • 10.0.0 up to but excluding 10.0.14393.4825 (affected)
MicrosoftWindows 7
  • 6.1.0 up to but excluding 6.1.7601.25796 (affected)
MicrosoftWindows 7 Service Pack 1
  • 6.1.0 up to but excluding 6.1.7601.25796 (affected)
MicrosoftWindows 8.1
  • 6.3.0 up to but excluding 6.3.9600.20207 (affected)
MicrosoftWindows Server 2008 Service Pack 2
  • 6.0.0 up to but excluding 6.0.6003.21309 (affected)
MicrosoftWindows Server 2008 Service Pack 2 (Server Core installation)
  • 6.0.0 up to but excluding 6.0.6003.21309 (affected)
MicrosoftWindows Server 2008 Service Pack 2
  • 6.0.0 up to but excluding 6.0.6003.21309 (affected)
MicrosoftWindows Server 2008 R2 Service Pack 1
  • 6.1.0 up to but excluding 6.1.7601.25796 (affected)
MicrosoftWindows Server 2008 R2 Service Pack 1 (Server Core installation)
  • 6.0.0 up to but excluding 6.1.7601.25796 (affected)
MicrosoftWindows Server 2012
  • 6.2.0 up to but excluding 6.2.9200.23545 (affected)
  • 6.2.0 up to but excluding 6.2.9200.23540 (affected)
MicrosoftWindows Server 2012 (Server Core installation)
  • 6.2.0 up to but excluding 6.2.9200.23545 (affected)
  • 6.2.0 up to but excluding 6.2.9200.23540 (affected)
MicrosoftWindows Server 2012 R2
  • 6.3.0 up to but excluding 6.3.9600.20207 (affected)
MicrosoftWindows Server 2012 R2 (Server Core installation)
  • 6.3.0 up to but excluding 6.3.9600.20207 (affected)

Timeline

  1. 15 Dec 2021 Published
  2. 6 Oct 2025 CVE-2021-43226 added to CISA KEV
  3. 6 Oct 2025 Added to the CISA KEV catalogue

References