May 2026: Windows TCP/IP Denial of Service Vulnerability
CVE-2026-40401 Published on May 12, 2026

Windows TCP/IP Denial of Service Vulnerability
Null pointer dereference in Windows TCP/IP allows an unauthorized attacker to deny service locally.

Vendor Advisory NVD

Weakness Type

NULL Pointer Dereference

A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit. NULL pointer dereference issues can occur through a number of flaws, including race conditions, and simple programming omissions.

Products Associated with CVE-2026-40401

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Microsoft Windows 10

Microsoft Windows Server 2019

Microsoft Windows Server 2022

Microsoft Windows Server 2025

Microsoft Windows 11 25h2

Microsoft Windows 11 23h2

Microsoft Windows Server 23h2

Microsoft Windows 11 24h2

Microsoft Windows 11 26h1

Microsoft Windows Server 2016

Microsoft Windows Server 2012

Microsoft Windows Server 2012 R2

Affected Versions

Microsoft Windows 10 Version 1607:

Version 10.0.14393.0 and below 10.0.14393.9140 is affected.

Microsoft Windows 10 Version 1809:

Version 10.0.17763.0 and below 10.0.17763.8755 is affected.

Microsoft Windows 10 Version 21H2:

Version 10.0.19044.0 and below 10.0.19044.7291 is affected.

Microsoft Windows 10 Version 22H2:

Version 10.0.19045.0 and below 10.0.19045.7291 is affected.

Microsoft Windows 11 version 22H3:

Version 10.0.22631.0 and below 10.0.22631.7079 is affected.

Microsoft Windows 11 Version 23H2:

Version 10.0.22631.0 and below 10.0.22631.7079 is affected.

Microsoft Windows 11 Version 24H2:

Version 10.0.26100.0 and below 10.0.26100.8457 is affected.

Microsoft Windows 11 Version 25H2:

Version 10.0.26200.0 and below 10.0.26200.8457 is affected.

Microsoft Windows 11 version 26H1:

Version 10.0.28000.0 and below 10.0.28000.2113 is affected.

Microsoft Windows Server 2012:

Version 6.2.9200.0 and below 6.2.9200.26079 is affected.

Microsoft Windows Server 2012 (Server Core installation):

Version 6.2.9200.0 and below 6.2.9200.26079 is affected.

Microsoft Windows Server 2012 R2:

Version 6.3.9600.0 and below 6.3.9600.23181 is affected.

Microsoft Windows Server 2012 R2 (Server Core installation):

Version 6.3.9600.0 and below 6.3.9600.23181 is affected.

Microsoft Windows Server 2016:

Version 10.0.14393.0 and below 10.0.14393.9140 is affected.

Microsoft Windows Server 2016 (Server Core installation):

Version 10.0.14393.0 and below 10.0.14393.9140 is affected.

Microsoft Windows Server 2019:

Version 10.0.17763.0 and below 10.0.17763.8755 is affected.

Microsoft Windows Server 2019 (Server Core installation):

Version 10.0.17763.0 and below 10.0.17763.8755 is affected.

Microsoft Windows Server 2022:

Version 10.0.20348.0 and below 10.0.20348.5139 is affected.

Microsoft Windows Server 2022, 23H2 Edition (Server Core installation):

Version 10.0.25398.0 and below 10.0.25398.2330 is affected.

Microsoft Windows Server 2025:

Version 10.0.26100.0 and below 10.0.26100.32860 is affected.

Microsoft Windows Server 2025 (Server Core installation):

Version 10.0.26100.0 and below 10.0.26100.32860 is affected.

May 2026: Windows TCP/IP Denial of Service VulnerabilityCVE-2026-40401 Published on May 12, 2026

Weakness Type

NULL Pointer Dereference

Products Associated with CVE-2026-40401

Affected Versions

May 2026: Windows TCP/IP Denial of Service Vulnerability
CVE-2026-40401 Published on May 12, 2026