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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-2021-42287

Microsoft Active Directory Domain Services Privilege Escalation Vulnerability

Recommended action

Validate affected assets and exposure now, then remediate on an accelerated schedule. Apply updates per vendor instructions.

View response plan
CVSS7.5
EPSS74.3%
KEVYes
ExploitationConfirmed exploitation
PatchPatch or guidance available ↓

Assessment

Why it matters

CISA lists this vulnerability as known to be exploited; exploitation is confirmed; EPSS is 74.3%; 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. Apply updates per vendor instructions.
  4. Review relevant security telemetry for evidence of attempted or successful exploitation.
  5. Document the remediation decision and track it to verified completion.

Vendor remediation

Patch and remediation links

Use the vendor source below to confirm the correct fixed version, package or mitigation for your affected product.

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-269
Affected versions
Microsoft Active Directory; Microsoft Windows Server 2004 (End Excluding: 10.0.19041.1348); Microsoft Windows Server 2008 (Version: r2); Microsoft Windows Server 2012 (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)
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: 74.3%
  4. Signal calculated at 83

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.