7.8

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

CVSS: 7.8v3.1HighKEVRansomwareAnalyzed
Published 15-09-2021Last modified 10-08-2026
Open JSON

Vulnerability summary

CVE-2021-36955 is a high (CVSS 7.8) vulnerability in Microsoft Windows. It is known to be exploited: CISA lists it, first on 03-11-2021. It has been used in ransomware campaigns. EPSS estimates a 4.07% chance of exploitation in the next 30 days, higher than 90.5% of scored vulnerabilities.

Overall risk
90/100
0100
Critical · default modelHow is this calculated?
CVSS score
7.8/10
010
High · v3.1 (CVE.org)
EPSS score
4.07%
0%100%
Low · +0.03 pp in 30 days
KEVListedCISA
RansomwareKnown useFlagged by CISA
Public exploits0No public exploits recorded

Timeline

  1. 15-09-2021
    PublishedVulnerability first disclosed.
  2. 03-11-2021
    Added to CISA KEVMicrosoft Windows Common Log File System (CLFS) Driver Privilege Escalation Vulnerability
  3. 17-11-2021
    CISA remediation dueApply updates per vendor instructions.
  4. 10-08-2026
    Last modifiedVulnerability information updated.

Description

Windows Common Log File System Driver Elevation of Privilege Vulnerability

CVSS metrics

3 scores · 2 sources · 2 versions

EPSS trend

Probability

4.07%

Chance of exploitation in the next 30 days

Percentile

91%

Versus all other CVEs

30-day change

+0.03 pp

From 4.04% on 19-09-2026

19-09-202619-10-2026
EPSS score
4.07%

Known exploited

Compare KEV catalogs
CISA KEVListed
Added
03-11-2021
Federal due date
17-11-2021
Ransomware

CISA required action

Apply updates per vendor instructions. nvd.nist.gov/vuln/detail/CVE-2021-36955

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

No weakness data has been published for this record.

Affected systems

Microsoft36 products

1 vendor · 36 products

References

3 links