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Microsoft Security Response CenterCVE-2026-40405

Windows TCP/IP Denial of Service Vulnerability

HighVendor CVSS 7.5 / 10 1 CVE Published May 12, 2026 at 7:00 AM UTC

Summary

Null pointer dereference in Windows TCP/IP allows an unauthorized attacker to deny service over a network.

Products covered

  • 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

Remediation

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

Vendor-listed fixes

  • 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

CVEs in this advisory 1

Updates

  1. Published by Microsoft Security Response Center

    The publication date reported by the vendor.

  2. Added to SecurityAlert

    We collected the advisory from the official source.

  3. Confirmed at the source

    Our collector saw this advisory during a later source check.