7.8

CVE-2021-43226: Microsoft Windows Privilege Escalation Vulnerability

CVSS: 7.8v3.1HighKEVRansomwareAnalyzed
Published 15-12-2021Last modified 22-08-2026
Open JSON

Vulnerability summary

CVE-2021-43226 is a high (CVSS 7.8) vulnerability in Microsoft Windows. It is known to be exploited: CISA lists it, first on 06-10-2025. It has been used in ransomware campaigns. EPSS estimates a 3.28% chance of exploitation in the next 30 days, higher than 88.2% 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
3.28%
0%100%
Low · +0.20 pp in 30 days
KEVListedCISA
RansomwareKnown useFlagged by CISA
Public exploits0No public exploits recorded

Timeline

  1. 15-12-2021
    PublishedVulnerability first disclosed.
  2. 06-10-2025
    Added to CISA KEVMicrosoft Windows Privilege Escalation Vulnerability
  3. 27-10-2025
    CISA remediation dueApply mitigations per vendor instructions.
  4. 22-08-2026
    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

3.28%

Chance of exploitation in the next 30 days

Percentile

88%

Versus all other CVEs

30-day change

+0.20 pp

From 3.07% on 19-09-2026

19-09-202619-10-2026
EPSS score
3.28%

Known exploited

Compare KEV catalogs
CISA KEVListed
Added
06-10-2025
Federal due date
27-10-2025
Ransomware

CISA required action

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. msrc.microsoft.com/update-guide/vulnerability/CVE-2021-43226 nvd.nist.gov/vuln/detail/CVE-2021-43226

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

No weakness data has been published for this record.

Affected systems

Microsoft41 products

1 vendor · 41 products

References

2 links