Is CVE-2021-42278 being actively exploited?

Yes. CVE-2021-42278 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, added on April 11, 2022.

What is the CVSS score for CVE-2021-42278?

CVE-2021-42278 has a CVSS 3.1 base score of 7.5 (HIGH).

CVE-2021-42278

HIGH · CVSS 7.5CISA KEV: actively exploitedEPSS 73.3%EU EUVD: exploited

Active Directory Domain Services Elevation of Privilege Vulnerability

Key facts

CVSS score: 7.5 (v3.1)
Severity: HIGH
CVSS vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS score: 73.3% (99th percentile)
In CISA KEV: Yes, added April 11, 2022
In EU EUVD: Yes (EUVD-2021-29254)
Published: November 10, 2021
NVD last modified: August 19, 2026
Status: Analyzed

CISA Known Exploited Vulnerability

Microsoft Active Directory Domain Services Privilege Escalation Vulnerability

Added to the KEV catalog on April 11, 2022; federal remediation due May 2, 2022. Known to be used in ransomware campaigns.

EU Vulnerability Database (EUVD)

This vulnerability is also tracked by ENISA as EUVD-2021-29254 in the EU Vulnerability Database. ENISA flags it as known exploited. Last updated in EUVD on August 19, 2026.

View on the EU Vulnerability Database

Affected products

microsoft / windows server 2004
microsoft / windows server 2008
microsoft / windows server 2008
microsoft / windows server 2012
microsoft / windows server 2012
microsoft / windows server 2016
microsoft / windows server 2019
microsoft / windows server 2022
microsoft / windows server 20h2

Certified products that may be affected

1 FIPS 140 or Common Criteria certified product, from automated matching by sec-certs.org.

Microsoft Windows 10 version 2004 (May 2020 Update), Microsoft Windows Server version 2004 (May 2020 Update) and others - Microsoft Corporation - Common Criteria 2020-50-INF-3671 - active

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-42278(Patch, Vendor Advisory)
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-42278(Patch, Vendor Advisory)
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-42278(US Government Resource)

Last updated September 17, 2026 · Source: NVD, CISA KEV, FIRST.org EPSS

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