CVE-2021-42278: Microsoft Active Directory Domain Services Privilege Escalation Vulnerability

Is it exploited?

Yes. CISA added it to the Known Exploited Vulnerabilities catalog on 11 Apr 2022, 152 days after the CVE record was published.

How likely is exploitation in the next 30 days?

73.3%

EPSS score, percentile 99.5 of all scored records

How severe?

7.5 High

CVSS v3.1 base score, given by the CNA

What should I do?

CISA deadline 2 May 2022. Apply updates per vendor instructions.

Advisories and patches (1)

Which versions are affected?

Affected

• from 6.1.7601.0 to before 6.1.7601.25769
• from 6.1.7601.0 to before 6.1.7601.25769
• from 6.0.6003.0 to before 6.0.6003.21282
• from 6.0.6003.0 to before 6.0.6003.21282
• from 6.2.9200.0 to before 6.2.9200.23517
• from 6.2.9200.0 to before 6.2.9200.23517

and 9 more in the table below

Versions by product

Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.

What to do

CISA due date for this action: 2 May 2022.

Advisories and patches

• Active Directory Domain Services Elevation of Privilege Vulnerability (Vendor advisory, Patch)

Linked from CISA's catalog entry

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

Affected products and versions

As listed in the CVE record.

Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.

About this vulnerability

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

Summary: CISA's KEV catalog, as of 28 Oct 2026.

• CISA added CVE-2021-42278 to its Known Exploited Vulnerabilities (KEV) catalog on 11 Apr 2022.
• CISA marks it as known to be used in ransomware campaigns.
• The due date CISA sets for the required action is 2 May 2022.
• The CVE record was published on 10 Nov 2021, 152 days before it was added to KEV.
• The CVE record carries a CVSS v3.1 base score of 7.5 (High), given by its CNA.
• FIRST's EPSS model puts the probability of exploitation in the next 30 days at 73.3% (percentile 99.5), as of 28 Oct 2026.
• CISA's SSVC assessment in the CVE record: exploitation active, automatable no, technical impact total.

Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026. About the data.

Description

Active Directory Domain Services Elevation of Privilege Vulnerability

Active Directory Domain Services Elevation of Privilege Vulnerability

Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.

Weakness

• CWE-20

CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record and the KEV entry.

Timeline

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