CISA KEV · Known exploitedHigh

CVE-2021-43226

Microsoft Windows

CVE-2021-43226 affects Microsoft Windows. Review the CVSS score, exploitation signals, affected versions, remediation status, and linked source material before making a change.

CVSS: 7.8
EPSS: 3.07%
CISA KEV: Listed
Published: 2021.12.16

PRIORITY ASSESSMENT

Immediate review

CISA has listed this vulnerability in the Known Exploited Vulnerabilities catalog.

Known exploitationConfirmed by CISA KEV

Exploit probability3.07%

Technical severityCVSS 7.8

Vulnerability overview

CVE-2021-43226 affects Microsoft Windows. Review the CVSS score, exploitation signals, affected versions, remediation status, and linked source material before making a change.

Affected product and versions

Product: Microsoft Windows
Affected versions: 10.0.0, 6.1.0, 6.3.0, 6.0.0, 6.2.0, < 10.0.10240.19145, < 10.0.14393.4825, < 10.0.17763.2366, < 10.0.18363.1977, < 10.0.19041.1415, < 10.0.19042.1415, < 10.0.19043.1415, < 10.0.19044.1415, < 10.0.22000.376, r2, < 10.0.20348.405
Fixed versions: 10.0.10240.19145, 10.0.14393.4825, 10.0.17763.2366, 10.0.18363.1977, 10.0.19041.1415, 10.0.19042.1415, 10.0.19043.1415, 10.0.19044.1415, 10.0.22000.376, 10.0.20348.405

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide

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.

Due date: 2025.10.27

1
Identify
Confirm that Microsoft Windows and an affected version are present.
2
Prioritize
Combine exploitation signals with asset exposure and business criticality.
3
Remediate
Follow the vendor advisory or supported update path and preserve rollback options.
4
Verify
Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CWE: Not available
KEV added: 2025.10.06
Ransomware use: 미확인