Windows DHCP Server: Heap-based buffer overflow enables local privilege escalation

Summary

A heap-based buffer overflow in the Windows DHCP Server component allows an authorized attacker to elevate privileges on the affected host. The attack requires local access and a valid low-privilege account on the system. Successful exploitation could give the attacker high impact on confidentiality, integrity and availability of the host (CVSS 3.1: 7.8, vector AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H).

Affected

• Windows 10 Version 1607: 10.0.14393.0 to below 10.0.14393.9612
• Windows 10 Version 1809: 10.0.17763.0 to below 10.0.17763.9376
• Windows 10 Version 21H2: 10.0.19044.0 to below 10.0.19044.7807
• Windows 10 Version 22H2: 10.0.19045.0 to below 10.0.19045.7807
• Windows 11 Version 23H2: 10.0.22631.0 to below 10.0.22631.7652
• Windows 11 Version 24H2: 10.0.26100.0 to below 10.0.26100.9711
• Windows 11 Version 25H2: 10.0.26200.0 to below 10.0.26200.9711
• Windows 11 Version 26H1: 10.0.28000.0 to below 10.0.28000.3231
• Windows 11 Version 26H2: 10.0.26300.0 to below 10.0.26300.9711
• Windows Server 2012 and Server Core installation: 6.2.9200.0 to below 6.2.9200.26434
• Windows Server 2012 R2 and Server Core installation: 6.3.9600.0 to below 6.3.9600.23470
• Windows Server 2016: 10.0.14393.0 to below 10.0.14393.9612

Fixed in

• Install the Microsoft security update for CVE-2026-83691 for your Windows version, using the fixed builds listed in the MSRC Security Update Guide.
• Windows 10 Version 1607 and Windows Server 2016: 10.0.14393.9612 or later.
• Windows 10 Version 22H2: 10.0.19045.7807 or later.
• Windows Server 2025 (Windows 11 24H2 build family): 10.0.26100.33650 or later according to secondary sources; verify on MSRC.
• KB numbers: check the MSRC Security Update Guide.

Workaround

Unknown.

Exploitation

• Microsoft rates exploit maturity as Unproven and states that the vulnerability is not publicly disclosed.
• CISA SSVC assessment: exploitation none, automatable no, technical impact total.
• No reports of exploitation in the wild were found in the research sources. This is based on limited searching and is not proof that exploitation does not occur.

Our recommendation

• Patch all affected Windows systems, starting with Windows 10 Version 1607 and Windows Server 2016 and any host running the DHCP Server role.
• Inventory your hosts to find Windows 10 1607 systems and DHCP Server role instances.
• Remove the DHCP Server role from hosts that do not need it.
• Restrict local logon to trusted accounts on affected hosts.
• Verify the Windows 10 1607 lifecycle status with Microsoft (not verified in this entry). If no fix is available for your version, plan an upgrade or Extended Security Updates.
• Monitor for unusual local privilege changes and new administrative accounts.

Public exploits iAttack code is publicly available (PoC on GitHub, Metasploit or Exploit-DB).

PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.

Research sources

• MSRC Security Update Guide: CVE-2026-83691 msrc.microsoft.com
• Vulners: MSRC data, fixed builds (MS:CVE-2026-83691) vulners.com
• Vulners: NVD mirror (NVD:CVE-2026-83691) vulners.com
• OpenCVE: CVE-2026-83691 app.opencve.io

Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 2 Nov 2026, 03:21.