CVE-2021-36955 kev+ ransomware in the critical feed json
Windows Common Log File System Driver Elevation of Privilege Vulnerability
published 2021-09-15 5 y ago modified 2026-08-10 2 mo ago also EUVD-2021-23531
- cvss
- 7.8
- version 3.1, CNA
- cisa kev
- Exploited
- added 2021-11-03, used in ransomware
- epss
- 4.1%
- EPSS 4.1% chance of exploitation in 30 days, percentile 90%
- public exploits
- 0
- none known
Summary
Windows Common Log File System Driver Elevation of Privilege Vulnerability
Patch / fix
cisa required action Apply updates per vendor instructions.
- Microsoft Windows 10 Version 1507 10.0.10240.19060
- Microsoft Windows 10 Version 1607 10.0.14393.4651
- Microsoft Windows 10 Version 1809 10.0.17763.2183
- Microsoft Windows 10 Version 1909 10.0.18363.1801
- Microsoft Windows 10 Version 2004 10.0.19041.1237
- Microsoft Windows 10 Version 20H2 10.0.19042.1237
- Microsoft Windows 10 Version 21H1 10.0.19043.1237
- Microsoft Windows 7 6.1.7601.25712
- Microsoft Windows 7 Service Pack 1 6.1.7601.25712
- Microsoft Windows 8.1 6.3.9600.20120
- Microsoft Windows Server 2008 R2 Service Pack 1 6.1.7601.25712
- Microsoft Windows Server 2008 R2 Service Pack 1 (Server Core installation) 6.1.7601.25712
- Microsoft Windows Server 2008 Service Pack 2 6.0.6003.21218
- Microsoft Windows Server 2008 Service Pack 2 (Server Core installation) 6.0.6003.21218
- Microsoft Windows Server 2012 6.2.9200.23462
- Microsoft Windows Server 2012 (Server Core installation) 6.2.9200.23462
- Microsoft Windows Server 2012 R2 6.3.9600.20120
- Microsoft Windows Server 2012 R2 (Server Core installation) 6.3.9600.20120
- Microsoft Windows Server 2016 10.0.14393.4651
- Microsoft Windows Server 2016 (Server Core installation) 10.0.14393.4651
- Microsoft Windows Server 2019 10.0.17763.2183
- Microsoft Windows Server 2019 (Server Core installation) 10.0.17763.2183
- Microsoft Windows Server 2022 10.0.20348.230
- Microsoft Windows Server version 2004 10.0.19041.1237
- Microsoft Windows Server version 20H2 10.0.19042.1237
Timeline
- Published
- Added to CISA KEV
- CISA patch deadline
- CISA SSVC: exploitation active
Known exploited
- Added
- 5 y ago
- Patch by
- 2021-11-17 (4 y ago)
- Ransomware
- Known to be used in ransomware campaigns
- Required action
- Apply updates per vendor instructions.
- Vendor, product
- Microsoft, Windows
- CISA name
- Microsoft Windows Common Log File System (CLFS) Driver Privilege Escalation Vulnerability
CISA SSVC
- Exploitation
- Active, exploited in the wild
- Automatable
- no
- Technical impact
- total
- Assessed
- 21 mo ago
Exploit prediction
4.07% chance of exploitation in the next 30 days, higher than 90% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 7.8 | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C |
| CNA | 3.1 | 7.8 | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H |
| NVD | 2.0 | 4.6 | AV:L/AC:L/Au:N/C:P/I:P/A:P |
Affected products
- Microsoft Windows 10 Version 1507
- Microsoft Windows 10 Version 1607
- Microsoft Windows 10 Version 1809
- Microsoft Windows 10 Version 1909
- Microsoft Windows 10 Version 2004
- Microsoft Windows 10 Version 20H2
- Microsoft Windows 10 Version 21H1
- Microsoft Windows 7
- Microsoft Windows 7 Service Pack 1
- Microsoft Windows 8.1
- Microsoft Windows Server 2008 R2 Service Pack 1
- Microsoft Windows Server 2008 R2 Service Pack 1 (Server Core installation)
- Microsoft Windows Server 2008 Service Pack 2
- Microsoft Windows Server 2008 Service Pack 2 (Server Core installation)
- Microsoft Windows Server 2012
- Microsoft Windows Server 2012 (Server Core installation)
- Microsoft Windows Server 2012 R2
- Microsoft Windows Server 2012 R2 (Server Core installation)
- Microsoft Windows Server 2016
- Microsoft Windows Server 2016 (Server Core installation)
- Microsoft Windows Server 2019
- Microsoft Windows Server 2019 (Server Core installation)
- Microsoft Windows Server 2022
- Microsoft Windows Server version 2004
- Microsoft Windows Server version 20H2
References
-
msrc.microsoft.com
/update-guide/vulnerability/CVE-2021-36955
vendor-advisory, patch
-
portal.msrc.microsoft.com
/en-US/security-guidance/advisory/CVE-2021-36955
patch, vendor-advisory
-
cisa.gov
/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-36955
government-resource, us-government-resource
Sources
- CVE List CVE-2021-36955
- NVD CVE-2021-36955
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.