CISA KEV advisory infographic for CVE-2021-43226: Windows CLFS driver icon with buffer overflow exploit arrow leading to SYSTEM privilege escalation, affected OS badges (Windows 10/11, Server 2016/2019/2022), October 27 2025 patch deadline calendar, log m

CISA added Microsoft Windows privilege escalation vulnerability CVE-2021-43226 to its Known Exploited Vulnerabilities (KEV) catalog on October 6, 2025, urging immediate patching due to active exploitation. The flaw in the Common Log File System (CLFS) Driver allows local authenticated attackers to elevate privileges to SYSTEM level via buffer overflows triggered by malicious CLFS log files, requiring only standard user access—ideal for post-initial-breach escalation in enterprises.

CISA KEV advisory infographic for CVE-2021-43226: Windows CLFS driver icon with buffer overflow exploit arrow leading to SYSTEM privilege escalation, affected OS badges (Windows 10/11, Server 2016/2019/2022), October 27 2025 patch deadline calendar, log mCISA KEV advisory infographic for CVE-2021-43226: Windows CLFS driver icon with buffer overflow exploit arrow leading to SYSTEM privilege escalation, affected OS badges (Windows 10/11, Server 2016/2019/2022), October 27 2025 patch deadline calendar, log m

It impacts Windows 10/11 and Servers 2016/2019/2022, with proof-of-concept exploits circulating on underground forums.

Federal agencies and critical infrastructure must remediate by October 27, 2025, per BOD 22-01, applying patches through Windows Update or WSUS, prioritizing domain controllers and file servers.

CISA KEV advisory infographic for CVE-2021-43226: Windows CLFS driver icon with buffer overflow exploit arrow leading to SYSTEM privilege escalation, affected OS badges (Windows 10/11, Server 2016/2019/2022), October 27 2025 patch deadline calendar, log mCISA KEV advisory infographic for CVE-2021-43226: Windows CLFS driver icon with buffer overflow exploit arrow leading to SYSTEM privilege escalation, affected OS badges (Windows 10/11, Server 2016/2019/2022), October 27 2025 patch deadline calendar, log m

For unpatchable systems, use Application Control and Windows Defender Exploit Guard as interim measures. Monitor Event IDs 4656/4658 for suspicious CLFS activity (e.g., clfs.sys, clfsw32.dll), and scan networks with Microsoft Baseline Security Analyzer or similar tools to identify exposures amid rising ransomware threats.


NPAV offers a robust solution to combat cyber fraud. Protect yourself with our top-tier security product, Z Plus Security