CVE-2021-43226

HIGH7.8

CISA KEV

Published 2021-12-15 · Updated 2026-08-22 · Source secure@microsoft.com

Summary

CVE-2021-43226 is a high-severity (CVSS 7.8) vulnerability in Microsoft Windows. CISA added it to the Known Exploited Vulnerabilities catalog on October 6, 2025, which means exploitation in the wild has been confirmed; US federal agencies had to remediate it by October 27, 2025. CISA also lists it as known to be used in ransomware campaigns, so it should be prioritised accordingly. Microsoft has 390 vulnerabilities in the KEV catalog, 117 of them linked to ransomware.

All 390 known-exploited Microsoft vulnerabilities →

Description

Windows Common Log File System Driver Elevation of Privilege Vulnerability

CVSS vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CISA Known-Exploited Vulnerability

Product: Microsoft — Windows

Name: Microsoft Windows Privilege Escalation Vulnerability

Date added: 2025-10-06 · Due: 2025-10-27

USED IN RANSOMWARE

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.

References

View on NVD

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