High MSRC-CVE-2026-40405 1 CVE

Windows TCP/IP Denial of Service Vulnerability

Published May 12, 2026 · Updated May 12, 2026

Vendor: Microsoft

Summary

Impact: Denial of Service. Microsoft rating: Important. Not known to be exploited — Exploitation Less Likely. Customer action: Required.

Details

Security updates
10.0.26100.32860 — https://support.microsoft.com/help/5087539
10.0.26100.32772 — https://support.microsoft.com/help/5087423
10.0.26200.8457 — https://support.microsoft.com/help/5089549
10.0.26200.8390 — https://support.microsoft.com/help/5089466
10.0.28000.2113 — https://support.microsoft.com/help/5089548

Vulnerabilities 1

High 7.5

CVE-2026-40405

Windows TCP/IP Denial of Service Vulnerability

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

Microsoft Windows Server 2025 Windows Server 2025 (Server Core installation) Windows 11 Version 24H2 Windows

May 12, 2026

Revision history

2026-05-12 #1
Information published.

References

CVE-2026-40405 Windows TCP/IP Denial of Service Vulnerability - HTML
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40405
Microsoft Exploitability Index
https://www.microsoft.com/en-us/msrc/exploitability-index?rtc=1
Microsoft Support Lifecycle
https://support.microsoft.com/lifecycle
Common Vulnerability Scoring System
https://www.first.org/cvss