Microsoft Windows Privilege Escalation Vulnerability (CVE-2021-43226)
Severity: high · Patch status: patched · Since 2025-10-06 · CVE-2021-43226
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 added CVE-2021-43226 to its Known Exploited Vulnerabilities catalog on Oct 6, 2025, which means attackers are exploiting it in the wild. CISA reports known use in ransomware campaigns.
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.
- US federal agencies must remediate by Oct 27, 2025 (BOD 22-01); treat that as the outer limit.
Sources
All live incidents on Threat Watch
