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Microsoft Security Response CenterCVE-2026-33840

Win32k Elevation of Privilege Vulnerability

Use after free in Windows Win32K - ICOMP allows an authorized attacker to elevate privileges locally.

Read the vendor bulletin Get alerts for Windows Server 2025 (Server Core installation)
7.8CVSS out of 10High severity
Scope

What the vendor says is affected

  • Windows Server 2025 (Server Core installation)
  • Windows 11 Version 25H2 for ARM64-based Systems
  • Windows 11 Version 25H2 for x64-based Systems
  • Windows 11 Version 24H2 for ARM64-based Systems
  • Windows 11 Version 24H2 for x64-based Systems
  • Windows Server 2025
  • Windows 11 version 26H1 for x64-based Systems
  • Windows 11 Version 26H1 for ARM64-based Systems

Versions the vendor lists as fixed

  • 10.0.26100.32860
  • 10.0.26100.32772
  • 10.0.26200.8457
  • 10.0.26200.8390
  • 10.0.26100.8457
  • 10.0.26100.8390
  • 10.0.28000.2113
Next step

What the vendor recommends

Install KB5087539. Install KB5087423. Install KB5089549. Install KB5089466. Install KB5089548.

Review the complete instructions on the vendor's site
Timeline

When this advisory changed

  1. Published by Microsoft Security Response Center

    The publication date reported by the vendor.

  2. Updated by Microsoft Security Response Center

    The vendor changed the advisory after it was first published.

  3. Added to SecurityAlert

    We collected the advisory from the official source.

Vulnerabilities

CVEs named in this advisory

CVE-2026-33840View CVSS, KEV, EPSS, and threat context
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