Microsoft fixes a critical vulnerability in the Windows DHCP Server service

Do you think this report is well-written? *

Yes

Do you use this technology? *

Yes

Was this report useful to you?

Yes

We would be happy if you would describe:

The security services provided by CESNET are designed to provide significant support in ensuring the cybersecurity of connected organizations. Although we strive to provide quality and reliable services, it is not possible to guarantee absolute coverage of all security vulnerabilities. Our services should be seen as a complement to an organization's own security management, not as a replacement. The client bears ultimate responsibility for securing their environment.

This report was translated by AI; nobody has reviewed the translation yet. Original language: Slovak.

[TLP:CLEAR] Microsoft fixes a critical vulnerability in the Windows DHCP Server service

Microsoft fixes 1 critical vulnerability in the Windows DHCP Server service [1]. The vulnerability affects Windows 10 client systems (versions 1607 and 1809) and Windows Server operating systems in versions 2012, 2012 R2, 2016, 2019, 2022 and 2025 (including Server Core installations). Security fixes for all of these releases have been made available as part of the standard cumulative updates [1].

Windows DHCP Server - RCE (CVE-2026-56159)

CVSS 9.8 (Critical)

An unauthenticated remote attacker can, by sending a specially crafted packet to the DHCP server, trigger a heap buffer overflow and subsequently execute code [1].

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

More information:

CVE-2026-56159 at cve.org, NVD
CWE-122: Heap-based Buffer Overflow at cwe.mitre.org

The vulnerability was publicly disclosed 14. 7. 2026.

Report feedback

[TLP:CLEAR] Microsoft fixes a critical vulnerability in the Windows DHCP Server service

Windows DHCP Server - RCE (CVE-2026-56159)

CVSS 9.8 (Critical)

Links