CVE-2021-42278

CVE-2021-42278 is a high-severity vulnerability in Microsoft Windows Server 2004 with a CVSS 3.x base score of 7.5. It is listed in CISA's Known Exploited Vulnerabilities (KEV) catalog, confirming it has been exploited in the wild (added 2022-04-11).

Key facts

Description

Active Directory Domain Services Elevation of Privilege Vulnerability

CVE-2021-42278: Active Directory Domain Services Elevation of Privilege Vulnerability

AI-generated analysis based on the vulnerability data on this page.

Summary

CVE-2021-42278 is a high-severity elevation of privilege vulnerability in Active Directory Domain Services, published on November 10, 2021. The vulnerability carries a CVSS v3 score of 7.5 and a CVSS v2 score of 6.5.

Background

Active Directory Domain Services (AD DS) is a core Microsoft Windows Server component that provides directory services, authentication, and identity management for domain-joined systems within an enterprise network.

Root Cause

The vulnerability exists within Active Directory Domain Services. No CWE identifier has been assigned in the available data.

Impact

With a CVSS v3 score of 7.5 (HIGH), the vulnerability requires an attacker to have low privileges and network access, with high attack complexity and no user interaction required. Successful exploitation can result in high impact to confidentiality, integrity, and availability of the affected system.

Exploitation Walkthrough

An attacker with authenticated low-privilege access to the target network may be able to exploit this vulnerability to elevate privileges. The attack vector is network-based, requires no user interaction, and has been assigned an exploit maturity score of 4.

Ethics Note: This section describes the vulnerability from a defensive perspective. Do not attempt to exploit systems without explicit authorization.

Affected and Patched Versions

The following Windows Server versions are listed as affected:

  • Windows Server 2004
  • Windows Server 2008 SP2
  • Windows Server 2008 R2 SP1 (x64)
  • Windows Server 2012
  • Windows Server 2012 R2
  • Windows Server 2016
  • Windows Server 2019
  • Windows Server 2022
  • Windows Server 20h2

Patch information was not provided in the source data; consult the Microsoft Security Response Center advisory for current patch availability.

Remediation

  • Apply the latest security updates from Microsoft as referenced in the official advisory.
  • Implement network segmentation to limit exposure of domain controllers.
  • Enforce the principle of least privilege for all domain accounts.
  • Monitor for anomalous authentication and privilege escalation activity.

Detection

Monitor Active Directory logs for unusual authentication patterns, unexpected privilege changes, and suspicious account modifications. Review security event logs on domain controllers for indicators of compromise.

Assessment

This vulnerability is present in the CISA Known Exploited Vulnerabilities catalog with an addition date of April 11, 2022, and has been observed in ransomware campaigns. The EPSS score is 0.70207, placing it in the 99.3rd percentile for exploit probability. The high exploit maturity rating and confirmed in-the-wild exploitation indicate that prioritization for patching is warranted.

Key lessons:

  1. Vulnerabilities in core directory services infrastructure carry outsized risk due to widespread enterprise reliance on Active Directory.
  2. Confirmed exploitation by ransomware actors demands rapid response even when technical details are limited.

References

Frequently asked questions

What is CVE-2021-42278?
Active Directory Domain Services Elevation of Privilege Vulnerability
How severe is CVE-2021-42278?
CVE-2021-42278 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with high attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-42278 being actively exploited?
Yes. CVE-2021-42278 is on CISA's Known Exploited Vulnerabilities (KEV) catalog, added on 2022-04-11, which means active exploitation has been confirmed. It should be prioritised for remediation.
What products are affected by CVE-2021-42278?
CVE-2021-42278 primarily affects Microsoft Windows Server 2004. In total, 9 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-42278?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Because this CVE is known to be actively exploited, treat remediation as urgent — CISA KEV typically sets a short remediation deadline.
Does CVE-2021-42278 have an EU (EUVD) identifier?
Yes. CVE-2021-42278 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2021-29254. It is also flagged as exploited in the EUVD (since 2022-04-11).
When was CVE-2021-42278 published?
CVE-2021-42278 was published on 2021-11-10 and last updated on 2026-06-17.

References

Affected products (9)

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