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Weekly Signal
Live intelligence Updated 19 Aug 2026 · 20:27 UTC

Microsoft · Active Directory, Windows Server 2004, Windows Server 2008 +5 more

CVE-2021-42278

Microsoft Active Directory Domain Services Privilege Escalation Vulnerability

Recommended action

Validate affected assets and exposure now, then remediate on an accelerated schedule. Microsoft Security patch CVE-2021-42278

View response plan
CVSS7.5
EPSS70.2%
KEVYes
ExploitationConfirmed exploitation
RemediationExplicit patch identified ↓

Assessment

Why it matters

CISA lists this vulnerability as known to be exploited; exploitation is confirmed; EPSS is 70.2%; technical severity is CVSS 7.5.

Active Directory Domain Services Elevation of Privilege Vulnerability

Who should care

  • Teams operating Active Directory, Windows Server 2004, Windows Server 2008 +5 more
  • Vulnerability and exposure management teams
  • Security operations teams monitoring exploitation activity

Response plan

What I would do

  1. Confirm whether Active Directory, Windows Server 2004, Windows Server 2008 +5 more is present in the environment.
  2. Identify affected versions and establish whether vulnerable services are exposed or reachable.
  3. Microsoft Security patch CVE-2021-42278
  4. Review relevant security telemetry for evidence of attempted or successful exploitation.
  5. Document the remediation decision and track it to verified completion.

Treatment intelligence

Remediation intelligence

Not yet verified

Vendor sources are listed before government and third-party guidance. Confirm product applicability and change prerequisites before deployment.

Verification noteAutomated link verification has not completed for this guidance yet.

Patch

Required Action

Technical details

CVSS vector
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
CWE
CWE-20
Affected versions
Microsoft Active Directory; Microsoft Windows Server 2004 (End Excluding 10.0.19041.1348); Microsoft Windows Server 2008 (Version - | Version r2); Microsoft Windows Server 2012 (Version - | Version r2); Microsoft Windows Server 2016 (End Excluding 10.0.14393.4770); Microsoft Windows Server 2019 (End Excluding 10.0.17763.2300); Microsoft Windows Server 2022 (End Excluding 10.0.20348.350); Microsoft Windows Server 20h2 (End Excluding 10.0.19042.1348)
Fixed versions
Microsoft Windows Server 2004 (Fixed from 10.0.19041.1348); Microsoft Windows Server 2016 (Fixed from 10.0.14393.4770); Microsoft Windows Server 2019 (Fixed from 10.0.17763.2300); Microsoft Windows Server 2022 (Fixed from 10.0.20348.350); Microsoft Windows Server 20h2 (Fixed from 10.0.19042.1348)
Published
10 November 2021
Attack vector
Network
Privileges required
Low
User interaction
None

Signal timeline

  1. CVE published
  2. Added to CISA KEV
  3. Latest EPSS score: 70.2%
  4. Signal calculated at 82

External references

Live public intelligence This assessment combines public-source evidence. Validate the affected product, version and exposure against your own environment before making a risk decision.