How severe is CVE-2021-42278?

CVE-2021-42278 has a CVSS 3.1 base score of 7.5 (HIGH). EPSS estimates a 73.3% probability of exploitation in the next 30 days. It is listed in the CISA Known Exploited Vulnerabilities catalog.

noPac (CVE-2021-42278): Active Directory Domain Services Elevation of

Q: What is noPac?

noPac is the common name for CVE-2021-42278. Part of the noPac pair of Active Directory flaws; this CVE covers missing validation of machine account names (sAMAccountName spoofing). Combined with CVE-2021-42287, it lets a standard domain user obtain domain admin privileges.

CISA Known Exploited Vulnerabilities

Microsoft Active Directory Domain Services Privilege Escalation Vulnerability is confirmed as actively exploited and is listed in the CISA KEV catalog.

Added to KEV

2022-04-11

Remediation due

2022-05-02

Ransomware

Known use

Required action
Apply updates per vendor instructions.

CISA notes
https://nvd.nist.gov/vuln/detail/CVE-2021-42278

Also Known as noPac

Part of the noPac pair of Active Directory flaws; this CVE covers missing validation of machine account names (sAMAccountName spoofing). Combined with CVE-2021-42287, it lets a standard domain user obtain domain admin privileges.

Name sources

Description

Active Directory Domain Services Elevation of Privilege Vulnerability

Severity

CVSS 3.1 · CNA7.5 HIGH

CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C

SSVC · CISA-ADP

Exploitationactive

Automatableno

Technical impacttotal

Exploitation Context

as of October 15, 2026

All KEV statistics→

CISA added CVE-2021-42278 to the KEV catalog 152 days after its CVE record was published.
It is one of 391 Microsoft entries in the CISA KEV catalog, and one of 166 added in 2022.
Its current EPSS score (73.3%) is higher than that of 60% of CISA KEV entries.

Affected Products

Vendor	Product	Affected versions
Microsoft	Microsoft Windows Server 2008 R2 Service Pack 1	6.1.7601.0 to <6.1.7601.25769
Microsoft	Microsoft Windows Server 2008 R2 Service Pack 1 (Server Core installation)	6.1.7601.0 to <6.1.7601.25769
Microsoft	Microsoft Windows Server 2008 Service Pack 2	6.0.6003.0 to <6.0.6003.21282
Microsoft	Microsoft Windows Server 2008 Service Pack 2 (Server Core installation)	6.0.6003.0 to <6.0.6003.21282
Microsoft	Microsoft Windows Server 2012	6.2.9200.0 to <6.2.9200.23517
Microsoft	Microsoft Windows Server 2012 (Server Core installation)	6.2.9200.0 to <6.2.9200.23517
Microsoft	Microsoft Windows Server 2012 R2	6.3.9600.0 to <6.3.9600.20174
Microsoft	Microsoft Windows Server 2012 R2 (Server Core installation)	6.3.9600.0 to <6.3.9600.20174
Microsoft	Microsoft Windows Server 2016	10.0.14393.0 to <10.0.14393.4770
Microsoft	Microsoft Windows Server 2016 (Server Core installation)	10.0.14393.0 to <10.0.14393.4770
Microsoft	Microsoft Windows Server 2019	10.0.17763.0 to <10.0.17763.2300
Microsoft	Microsoft Windows Server 2019 (Server Core installation)	10.0.17763.0 to <10.0.17763.2300
Microsoft	Microsoft Windows Server 2022	10.0.20348.0 to <10.0.20348.350
Microsoft	Microsoft Windows Server version 2004	10.0.0 to <10.0.19041.1348
Microsoft	Microsoft Windows Server version 20H2	10.0.0 to <10.0.19042.1348

References

2 Links

Vendor advisories

Active Directory Domain Services Elevation of Privilege Vulnerability

Other references

https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-42278

Record Details

Published

2021-11-10

Last updated

2026-08-19

Assigner (CNA)

microsoft

Credited to

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CVE record data © The MITRE Corporation, used under the CVE Terms of Use. Exploited-in-the-wild data from the CISA Known Exploited Vulnerabilities catalog (CC0). Exploit prediction scores by FIRST EPSS (first.org/epss). This site is not endorsed or certified by MITRE, NVD, CISA, or FIRST.