Description
Access of resource using incompatible type ('type confusion') in Windows DHCP Server allows an unauthorized attacker to deny service over a network.
Published: 2026-09-08
Score: 7.5 High
EPSS: 1.2% Low
KEV: No
Impact: Denial of Service
Action: Immediate Patch
AI Analysis

Impact

An unauthorized attacker can exploit a type‑confusion flaw in the Windows DHCP Server that allows access to a resource using an incompatible type. The vulnerability can be leveraged to trigger a denial of service on the DHCP service over a network, causing legitimate clients to lose network connectivity. The primary weakness is identified as CWE-843, which indicates that incorrect type handling can lead to a service interruption.

Affected Systems

Microsoft Windows 10 Version 1607; Microsoft Windows 10 Version 1809; Microsoft Windows Server 2012; Microsoft Windows Server 2012 (Server Core installation); Microsoft Windows Server 2012 R2; Microsoft Windows Server 2012 R2 (Server Core installation); Microsoft Windows Server 2016; Microsoft Windows Server 2016 (Server Core installation); Microsoft Windows Server 2019; Microsoft Windows Server 2019 (Server Core installation); Microsoft Windows Server 2022; Microsoft Windows Server 2025; Microsoft Windows Server 2025 (Server Core installation).

Risk and Exploitability

The CVSS score of 7.5 denotes moderate‑to‑high severity, while the EPSS score is not available. The vulnerability is not listed in CISA's KEV catalog. Based on the description, it is inferred that the flaw can be triggered remotely by an attacker with access to the network to send a specially crafted DHCP packet, which would interrupt service availability for all clients associated with the vulnerable DHCP server.

Generated by OpenCVE AI on September 9, 2026 at 21:36 UTC.

Remediation

No vendor fix or workaround currently provided.

OpenCVE Recommended Actions

  • Apply the Microsoft patch that addresses CVE-2026-77889 as published in the Microsoft Security Response Center update guide.
  • Temporary mitigation: disable the DHCP Server service on affected machines until the patch can be applied, ensuring that no DHCP traffic gains service access during the vulnerability window.
  • Long‑term mitigation: implement network segmentation or firewall rules that restrict DHCP traffic to trusted hosts and monitor for anomalous DHCP requests that could indicate attempts to trigger type‑confusion exploits.

Generated by OpenCVE AI on September 9, 2026 at 21:36 UTC.

Tracking

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Advisories

No advisories yet.

History

Wed, 16 Sep 2026 15:15:00 +0000

Type Values Removed Values Added
CPEs cpe:2.3:o:microsoft:windows_10_1607:*:*:*:*:*:*:x64:*
cpe:2.3:o:microsoft:windows_10_1809:*:*:*:*:*:*:x64:*
cpe:2.3:o:microsoft:windows_server_2012:-:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_server_2012:r2:*:*:*:*:*:*:*

Sun, 13 Sep 2026 20:30:00 +0000

Type Values Removed Values Added
First Time appeared Microsoft windows Server 2012 (server Core Installation)
Microsoft windows Server 2012 R2
Microsoft windows Server 2012 R2 (server Core Installation)
Microsoft windows Server 2016 (server Core Installation)
Microsoft windows Server 2019 (server Core Installation)
Microsoft windows Server 2025 (server Core Installation)
Vendors & Products Microsoft windows Server 2012 (server Core Installation)
Microsoft windows Server 2012 R2
Microsoft windows Server 2012 R2 (server Core Installation)
Microsoft windows Server 2016 (server Core Installation)
Microsoft windows Server 2019 (server Core Installation)
Microsoft windows Server 2025 (server Core Installation)

Tue, 08 Sep 2026 20:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Tue, 08 Sep 2026 17:30:00 +0000

Type Values Removed Values Added
Description Access of resource using incompatible type ('type confusion') in Windows DHCP Server allows an unauthorized attacker to deny service over a network.
Title Windows DHCP Server Denial of Service Vulnerability
First Time appeared Microsoft
Microsoft windows 10 1607
Microsoft windows 10 1809
Microsoft windows Server 2012
Microsoft windows Server 2012 R2
Microsoft windows Server 2016
Microsoft windows Server 2019
Microsoft windows Server 2022
Microsoft windows Server 2025
Weaknesses CWE-843
CPEs cpe:2.3:o:microsoft:windows_10_1607:*:*:*:*:*:*:x86:*
cpe:2.3:o:microsoft:windows_10_1809:*:*:*:*:*:*:x86:*
cpe:2.3:o:microsoft:windows_server_2012:*:*:*:*:*:*:x64:*
cpe:2.3:o:microsoft:windows_server_2012_R2:*:*:*:*:*:*:x64:*
cpe:2.3:o:microsoft:windows_server_2016:*:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_server_2019:*:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_server_2022:*:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_server_2025:*:*:*:*:*:*:*:*
Vendors & Products Microsoft
Microsoft windows 10 1607
Microsoft windows 10 1809
Microsoft windows Server 2012
Microsoft windows Server 2012 R2
Microsoft windows Server 2016
Microsoft windows Server 2019
Microsoft windows Server 2022
Microsoft windows Server 2025
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C'}

Subscriptions

Microsoft Windows 10 1607 Windows 10 1809 Windows Server 2012 Windows Server 2012 (server Core Installation) Windows Server 2012 R2 Windows Server 2012 R2 Windows Server 2012 R2 (server Core Installation) Windows Server 2016 Windows Server 2016 (server Core Installation) Windows Server 2019 Windows Server 2019 (server Core Installation) Windows Server 2022 Windows Server 2025 Windows Server 2025 (server Core Installation)
cve-icon MITRE

Status: PUBLISHED

Assigner: microsoft

Published:

Updated: 2026-09-25T21:33:23.546Z

Reserved: 2026-08-21T17:26:55.611Z

Link: CVE-2026-77889

cve-icon Vulnrichment

Updated: 2026-09-08T18:56:03.457Z

cve-icon NVD

Status : Analyzed

Published: 2026-09-08T18:20:38.587

Modified: 2026-09-24T23:19:02.657

Link: CVE-2026-77889

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-13T20:11:05Z

Weaknesses
  • CWE-843

    Access of Resource Using Incompatible Type ('Type Confusion')