CVE-2021-36955Actively exploitedAdded to KEV 2021-11-03Known ransomware campaign use

Microsoft Windows Common Log File System (CLFS) Driver Privilege Escalation Vulnerability

Microsoft, Windows

Description

Microsoft Windows Common Log File System (CLFS) driver contains an unspecified vulnerability that allows for privilege escalation.

CVSS severity for this advisory hasn't been enriched from NVD yet, check back shortly.

EPSS, exploit probability

Medium

4.1%

estimated chance of real-world exploitation in the next 30 days, higher than 90.6% of every CVE FIRST.org scores

Refreshed 10/28/2026, via FIRST.org's EPSS model, not CVSS, this measures likelihood of exploitation, not how severe it would be.

Required action

Apply updates per vendor instructions.

CISA-recommended due date: 2021-11-17

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