# CVE-2021-36955: Microsoft Windows Common Log File System (CLFS) Driver Privilege Escalation Vulnerability

Source: https://junglewise.ai/threats/cve-2021-36955-microsoft-windows-common-log-file-system-clfs-driver-privilege  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2021-11-03. Updated: 2026-05-10  
License: CC BY 4.0 with a link back

CVE-2021-36955 · Severity: critical · CVSS 7.8 · Exploited in the wild · Published 2021-11-03

The Microsoft Windows Common Log File System (CLFS) driver contains an elevation of privilege vulnerability. An attacker who successfully exploits this vulnerability could gain SYSTEM privileges on the affected system. This vulnerability has been observed being exploited in the wild.

Technologies: [Microsoft Windows](https://junglewise.ai/threats/technologies/windows). Vendors: [Microsoft](https://junglewise.ai/threats/vendors/microsoft).

## Quick answers

**Is CVE-2021-36955 exploited in the wild?** Yes. CVE-2021-36955 is known to be exploited in the wild, first recorded on 3 November 2021. Treat it as urgent.

**How severe is CVE-2021-36955?** Critical severity, with a CVSS score of 7.8, published 3 November 2021.

**Which products and versions are affected?** Microsoft Windows 10 1507, 1607, 1809, 1909, 2004, 20H2, 21H1; Microsoft Windows 7 SP1; Microsoft Windows 8.1; Microsoft Windows RT 8.1; and 7 more.

**Is there a fix for CVE-2021-36955?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2021-36955 attacked?** It is attacked with local access, in an operating system.

**Am I affected by CVE-2021-36955?** Check whether you run Microsoft Windows. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Affected products

- Microsoft Windows 10 1507, 1607, 1809, 1909, 2004, 20H2, 21H1
- Microsoft Windows 7 SP1
- Microsoft Windows 8.1
- Microsoft Windows RT 8.1
- Microsoft Windows Server 2008 SP2, R2 SP1
- Microsoft Windows Server 2012 R2
- Microsoft Windows Server 2016
- Microsoft Windows Server 2019
- Microsoft Windows Server 2022
- Microsoft Windows Server 2004
- Microsoft Windows Server 20H2

## Timeline

- 2021-09-24: disclosed: Initial analysis by NIST
- 2021-11-03: kev added: Added to CISA Known Exploited Vulnerabilities Catalog
- 2021-11-03: advisory: Published date reported in advisory summary

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