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Microsoft Security Response CenterCVE-2026-40414

Windows TCP/IP Denial of Service Vulnerability

According to the CVSS score, the attack vector is adjacent (AV:A). What does this mean for this vulnerability? This attack is limited to systems connected to the same network segment as the attacker. The attack cannot be performed across multiple networks (for example, a WAN) and would be limited to systems on the same network switch or virtual network.

Read the vendor bulletin Get alerts for Windows
7.4CVSS out of 10High severity
Scope

What the vendor says is affected

  • Windows 10 Version 1809 for x64-based Systems
  • Windows Server 2019
  • Windows Server 2019 (Server Core installation)
  • Windows Server 2022
  • Windows Server 2022 (Server Core installation)
  • Windows 10 Version 21H2 for x64-based Systems
  • Windows 10 Version 22H2 for x64-based Systems
  • 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 23H2 for ARM64-based Systems
  • Windows 11 Version 23H2 for x64-based Systems
  • Windows Server 2022, 23H2 Edition (Server Core installation)
  • 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
  • Windows 10 Version 1607 for x64-based Systems
  • Windows Server 2016
  • Windows Server 2016 (Server Core installation)
  • Windows Server 2012
  • Windows Server 2012 (Server Core installation)
  • Windows Server 2012 R2

Versions the vendor lists as fixed

  • 10.0.17763.8755
  • 10.0.20348.5139
  • 10.0.20348.5074
  • 10.0.19044.7291
  • 10.0.19045.7417
  • 10.0.26100.32860
  • 10.0.26100.32772
  • 10.0.26200.8457
  • 10.0.26200.8390
  • 10.0.22631.7079
  • 10.0.22631.7219
  • 10.0.25398.2330
  • 10.0.26100.8457
  • 10.0.26100.8390
  • 10.0.28000.2113
  • 10.0.14393.9140
  • 6.2.9200.26079
  • 6.3.9600.23181
Next step

What the vendor recommends

Install KB5087538. Install KB5087545. Install KB5087424. Install KB5087544. Install KB5094127. Install KB5087539. Install KB5087423. Install KB5089549. Install KB5089466. Install KB5087420. Install KB5093998. Install KB5087541. Install KB5089548. Install KB5087537. Install KB5087470. Install KB5087471.

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. Added to SecurityAlert

    We collected the advisory from the official source.

Vulnerabilities

CVEs named in this advisory

CVE-2026-40414View CVSS, KEV, EPSS, and threat context
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