VulnerabilityAnalyzed
CVE-2021-36955
Microsoft Windows Common Log File System (CLFS) Driver Privilege Escalation Vulnerability
KEVHIGH 7.8EPSS 4.07%
Does this matter?
Known to be exploited in the wild (CISA KEV, CISA remediation deadline 17 November 2021). Treat as an emergency change: patch or isolate now, then hunt for prior compromise.
Description
Windows Common Log File System Driver Elevation of Privilege Vulnerability
- CVSS 3.1
- 7.8 HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- EPSS
- 4.07% probability · 91th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Listed 3 November 2021 · due 17 November 2021 · used in ransomware campaigns
- Affected
- microsoft/windows 10 1507 · microsoft/windows 10 1607 · microsoft/windows 10 1809 · microsoft/windows 10 1909 · microsoft/windows 10 2004 · microsoft/windows 10 20h2 · microsoft/windows 10 21h1 · microsoft/windows 7 · microsoft/windows 8.1 · microsoft/windows rt 8.1 · microsoft/windows server 2004 · microsoft/windows server 2008 · microsoft/windows server 2012 · microsoft/windows server 2016 · microsoft/windows server 2019 · microsoft/windows server 2022 · microsoft/windows server 20h2
- Source
- secure@microsoft.com
EPSS 4.1% since 30 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
CISA notes
Apply updates per vendor instructions. https://nvd.nist.gov/vuln/detail/CVE-2021-36955
References
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-36955Patch, Vendor Advisory
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-36955Patch, Vendor Advisory
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-36955US Government Resource
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.