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Vulnerabilities

Vulnerability · CVE-2021-42278

Microsoft Active Directory Domain Services Privilege Escalation Vulnerability

Published Nov 9, 2021 · catalog updated Aug 19, 2026 · Microsoft Active Directory

Patch now

CVE-2021-42278 is in the CISA known-exploited catalog, due May 2, 2022. Confirm Microsoft Active Directory against the vendor advisory and apply that fix. The CVSS score does not change the priority.

Gaps on this record

  • No version range is stored. A customer cannot check an installed version against this record.
Severity
High7.5
Known exploitation
CISA KEV and VulnCheck KEV
EPSS
73.30%
Remediation
Remediation guidance
Affected products
cpe microsoft/windows server 2004 · cpe microsoft/windows server 2008 · cpe microsoft/windows server 2012 · cpe microsoft/windows server 2016 · cpe microsoft/windows server 2019 · cpe microsoft/windows server 2022

Microsoft Active Directory Domain Services contains an unspecified vulnerability that allows for privilege escalation.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe microsoft/windows server 2004version unspecified
  • cpe microsoft/windows server 2008r2
  • cpe microsoft/windows server 2012r2
  • cpe microsoft/windows server 2016version unspecified
  • cpe microsoft/windows server 2019version unspecified
  • cpe microsoft/windows server 2022version unspecified
  • vendor Microsoft Active Directoryversion unspecified

How to fix CVE-2021-42278

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

CVE-2021-42278 is in the CISA known-exploited catalog, due May 2, 2022. Confirm Microsoft Active Directory against the vendor advisory and apply that fix. The CVSS score does not change the priority.

Which versions are affected?

Compare what you have installed with microsoft/windows server 2008 r2; microsoft/windows server 2012 r2. Apply updates per vendor instructions.

What should an analyst verify?

CWE-20: Improper Input Validation. EPSS 73.30%. The CISA KEV listing is the exploitation evidence. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Technology hubs

Windows security

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Nov 9, 2021 · Catalog

    Detected

    Microsoft Active Directory Domain Services contains an unspecified vulnerability that allows for privilege escalation.

  2. Apr 11, 2022 · CISA KEV

    Known exploited

    Apply updates per vendor instructions.

  3. May 2, 2022 · CISA KEV

    Remediation due

    Apply updates per vendor instructions.

  4. Aug 19, 2026 · Catalog

    Updated

    Microsoft Active Directory Domain Services contains an unspecified vulnerability that allows for privilege escalation.

Sources

  • CISA KEVConfirmed exploitationCVE-2021-42278

    Microsoft Active Directory Domain Services contains an unspecified vulnerability that allows for privilege escalation.

    cisa.gov
  • CVE.orgVulnerability recordCVE-2021-42278

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2021-42278

    30-day exploitation probability 73.3%

    first.org
  • NIST NVDVulnerability recordCVE-2021-42278

    Active Directory Domain Services Elevation of Privilege Vulnerability

    nvd.nist.gov
  • VulnCheck KEVConfirmed exploitationCVE-2021-42278

    Microsoft Active Directory Domain Services contains an unspecified vulnerability that allows for privilege escalation.

    vulncheck.com

References

Freshness

Last verified in this catalog Oct 17, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.