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CVE-2021-43226

Microsoft Windows Privilege Escalation

7.8 HIGHActively exploited (CISA KEV)Used in ransomwareEPSS 3.10%
  1. Published15 Dec 2021
  2. Added to CISA KEV6 Oct 2025
  3. Remediation due27 Oct 2025
Actively exploited (CISA KEV)

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

Added to KEV: 6 Oct 2025Federal remediation due: 27 Oct 2025Used in ransomware

Description

Windows Common Log File System Driver Elevation of Privilege Vulnerability

CVSS 3.1 breakdown

Attack vectorLocal
Attack complexityLow
Privileges requiredLow
User interactionNone
ScopeUnchanged
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected products

Microsoft Windows 10 1507< 10.0.10240.19145
Microsoft Windows 10 1607< 10.0.14393.4825
Microsoft Windows 10 1809< 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 21h2< 10.0.19044.1415
Microsoft Windows 11 21h2< 10.0.22000.376
Microsoft Windows 7all versions
Microsoft Windows 8.1all versions
Microsoft Windows Rt 8.1all versions
Microsoft Windows Server 2004< 10.0.19041.1415
Microsoft Windows Server 2008r2
Microsoft Windows Server 2012r2
Microsoft Windows Server 2016< 10.0.14393.4825
Microsoft Windows Server 2019< 10.0.17763.2366
Microsoft Windows Server 2022< 10.0.20348.405
Microsoft Windows Server 20h2< 10.0.19042.1415

Remediation

Fixed in
Microsoft Windows 10 1507≥ 10.0.10240.19145
Microsoft Windows 10 1607≥ 10.0.14393.4825
Microsoft Windows 10 1809≥ 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 21h2≥ 10.0.19044.1415
Microsoft Windows 11 21h2≥ 10.0.22000.376
Microsoft Windows Server 2004≥ 10.0.19041.1415

References

Frequently asked

Is CVE-2021-43226 being actively exploited?

Yes. CVE-2021-43226 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, added 6 Oct 2025. It has been used in ransomware campaigns.

How severe is CVE-2021-43226?

CVE-2021-43226 has a CVSS 3.1 base score of 7.8, rated high. EPSS estimates a 3.10% probability of exploitation.

Which products are affected by CVE-2021-43226?

Affected products include Microsoft Windows 10 1507, Microsoft Windows 10 1607, Microsoft Windows 10 1809, Microsoft Windows 10 1909, Microsoft Windows 10 2004, and 14 more.

How do I fix CVE-2021-43226?

Upgrade affected software to a fixed version, for example Microsoft Windows 10 1507 10.0.10240.19145, Microsoft Windows 10 1607 10.0.14393.4825, Microsoft Windows 10 1809 10.0.17763.2366 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2021-43226 against the real software inventory on every managed device, every day. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. Because it is on the CISA KEV list, Secuno flags any affected asset as top-priority automatically. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.