CVE-2026-42915: Windows TCP/IP Denial of Service Vulnerability

Overview

Severity

Medium (CVSS 5.7)

CVSS Vector

CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/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-Jun

Released

2026-06-09

Description

Incorrect calculation of buffer size in Windows TCP/IP allows an authorized attacker to deny service over an adjacent network.

FAQ

According to the CVSS metric, the attack vector is adjacent (AV:A). What does that mean for this vulnerability? An authenticated attacker could exploit this vulnerability with LAN access.

Affected Products (18)

Windows

• Windows Server 2022
• Windows Server 2022 (Server Core installation)
• Windows 10 Version 21H2 for 32-bit Systems
• Windows 10 Version 21H2 for ARM64-based Systems
• 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 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

ESU

• Windows 10 Version 22H2 for x64-based Systems
• Windows 10 Version 22H2 for ARM64-based Systems
• Windows 10 Version 22H2 for 32-bit Systems

Security Updates (6)

• 5094128
• 5094127
• 5094125
• 5094126
• 5093998
• 5095051

Acknowledgments

Anonymous, Calif.io and Milad Nasr (Anthropic) with Claude with Calif.io and Anthropic, <a href="https://x.com/_qwerty_po">Wongi Lee</a> with <a href="https://xint.io/">Theori</a>, <a href="https://x.com/physicube">Jungwoo Lee</a> with <a href="https://softsec.kaist.ac.kr/">KAIST SoftSec Lab</a>

Revision History

• 2026-06-09: Information published.