CVE-2026-56159: DHCP Server Service Remote Code Execution Vulnerability

Overview

Severity

Critical (CVSS 9.8)

CVSS Vector

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

Category

Remote Code Execution

Exploit Status

Not Exploited

Exploitation Likelihood

Unlikely

Patch Tuesday

2026-Jul

Released

2026-07-14

Description

Heap-based buffer overflow in Windows DHCP Server allows an unauthorized attacker to execute code over a network.

FAQ

How could an attacker exploit this vulnerability? An unauthenticated attacker could exploit this vulnerability by sending specially crafted packet to a Dynamic Host Configuration Protocol (DHCP) Server configured to provide data for Option 43.

Affected Products (15)

Windows

• Windows 10 Version 1809 for 32-bit Systems
• Windows 10 Version 1809 for x64-based Systems
• Windows Server 2019
• Windows Server 2019 (Server Core installation)
• Windows Server 2022
• Windows Server 2025 (Server Core installation)
• Windows Server 2025
• Windows 10 Version 1607 for 32-bit Systems
• Windows 10 Version 1607 for x64-based Systems
• Windows Server 2016
• Windows Server 2016 (Server Core installation)

ESU

• Windows Server 2012
• Windows Server 2012 (Server Core installation)
• Windows Server 2012 R2
• Windows Server 2012 R2 (Server Core installation)

Security Updates (6)

• 5099538
• 5099540
• 5099536
• 5099535
• 5099445
• 5099444

Acknowledgments

Lewis Lee

Revision History

• 2026-07-14: Information published.