CVE-2026-40413: Windows TCP/IP Denial of Service Vulnerability

Overview

Severity

High (CVSS 7.4)

CVSS Vector

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H/E:U/RL:O/RC:C

Category

Denial of Service

Exploit Status

Not Exploited

Exploitation Likelihood

Less Likely

Patch Tuesday

2026-May

Released

2026-05-12

Description

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

FAQ

According to the CVSS metric, a successful exploitation could lead to a scope change (S:C). What does this mean for this vulnerability? In this case, a successful attack could be performed from a low privilege Hyper-V guest. The attacker could traverse the guest's security boundary to cause denial of service on the Hyper-V host environment. 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.

Affected Products (25)

Windows

• 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 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)

ESU

• Windows 10 Version 22H2 for x64-based Systems
• Windows Server 2012
• Windows Server 2012 (Server Core installation)
• Windows Server 2012 R2
• Windows Server 2012 R2 (Server Core installation)

Security Updates (14)

• 5087538
• 5087545
• 5087424
• 5087544
• 5087539
• 5087423
• 5089549
• 5089466
• 5087420
• 5087541
• 5089548
• 5087537
• 5087470
• 5087471

Acknowledgments

Microsoft

Revision History

• 2026-05-12: Information published.