OTPulse

Windows DHCP Server Denial of Service Vulnerability

Plan PatchCVSS 7.5CVE-2026-77889Sep 8, 2026
Microsoft
IT in OT - Windows Server and Active Directory are widely deployed in OT environments
Attack path
Attack VectorNetwork
Auth RequiredNone
ComplexityLow
User InteractionNone needed
Summary

A type confusion vulnerability in Windows DHCP Server allows an unauthenticated attacker with network access to cause a denial of service by sending a malformed DHCP packet, crashing the DHCP service and preventing IP address assignment to network clients.

What this means
What could happen
An attacker can send malformed network traffic to a Windows DHCP server, causing it to crash and stop assigning IP addresses to devices on your network. This could leave critical infrastructure offline if you depend on DHCP for device connectivity.
Who's at risk
Windows Server systems (2016, 2019, 2022, 2025) and Windows 10 systems that run DHCP server role. This affects any organization using Windows-based DHCP for IP address assignment to workstations, servers, or network devices in OT environments.
How it could be exploited
An attacker with network access to your DHCP server port (UDP 67) sends a specially crafted DHCP request that exploits a type confusion flaw in the server code. The malformed packet causes the DHCP service to crash, denying service to all legitimate DHCP clients.
Prerequisites
  • Network access to DHCP server on UDP port 67
  • DHCP service enabled and running on the target server
remotely exploitableno authentication requiredlow complexityaffects network infrastructure
Exploitability
Some exploitation risk — EPSS score 1.2%
Affected products (12)
12 with fix
ProductAffected VersionsFix Status
Windows 10 Version 1809 for 32-bit SystemsAll versionsBuild 10.0.17763.9245
Windows 10 Version 1809 for x64-based SystemsAll versionsBuild 10.0.17763.9245
Windows Server 2019All versionsBuild 10.0.17763.9245
Windows Server 2019 (Server Core installation)All versionsBuild 10.0.17763.9245
Windows Server 2022All versionsBuild 10.0.20348.5622
Windows Server 2022 (Server Core installation)All versionsBuild 10.0.20348.5622
Windows Server 2025 (Server Core installation)All versionsBuild 10.0.26100.33438
Windows Server 2025All versionsBuild 10.0.26100.33438
Remediation & Mitigation
0/3
Do now
0/1
WORKAROUNDRestrict network access to UDP port 67 (DHCP) to only trusted internal subnets using firewall rules
Schedule — requires maintenance window
0/1

Patching may require device reboot — plan for process interruption

HOTFIXApply the September 2026 Windows security update to all affected Windows Server and Windows 10 systems running DHCP service
Long-term hardening
0/1
HARDENINGSegment DHCP servers from untrusted or external network segments
View full vendor advisory
API: /api/v1/advisories/5c932138-1f57-434b-9c6e-7fe7fee7c4f1

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Windows DHCP Server Denial of Service Vulnerability | CVSS 7.5 - OTPulse