CVE-2021-43226
Published: October 6, 2025
Official Description
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 KEV Advisory
Microsoft Windows Privilege Escalation Vulnerability
Microsoft Windows Common Log File System Driver contains a privilege escalation vulnerability that could allow a local, privileged attacker to bypass certain security mechanisms.
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Risk Analysis
This privilege escalation vulnerability in the Microsoft Windows Common Log File System Driver allows a local, privileged attacker to bypass security mechanisms. Its inclusion in CISA's KEV catalog and an EPSS score of 0.07549 confirm active exploitation and a high likelihood of future attacks.
This vulnerability is actively exploited in the wild, as confirmed by its presence in CISA's KEV catalog. Exploitation requires a local attacker with existing privileges.
Install the latest security updates from Microsoft to patch the Windows Common Log File System Driver. Implement strong access controls to limit privileged access on Windows systems.
Technical Analysis
CVE-2021-43226 requires local access, meaning attackers must already have a foothold on the target system.
Exploitation requires some privileges, which limits the exposure to scenarios where an attacker has already gained initial access.
CISA has added CVE-2021-43226 to the Known Exploited Vulnerabilities (KEV) catalog, confirming active exploitation in the wild. U.S. federal agencies are required to patch this within the mandated timeframe, and all organizations should treat remediation as urgent.
Affected Vendors & Products
Exploit & PoC Resources
All References (2)
Quick Facts
Recommended Actions
- →Apply vendor patches immediately
- →Monitor CVE-2021-43226 in threat intel feeds
- →Review IDS/IPS signatures for exploitation attempts
- !CISA KEV: Federal agencies must patch per BOD 22-01 timeline
- !Active exploitation confirmed — treat as P1