Windows UPnP Device Host: Heap-based buffer overflow allows local privilege escalation

Summary

A heap-based buffer overflow (CWE-122) in the Windows Universal Plug and Play (UPnP) Device Host allows an authorised local user to elevate privileges. Successful exploitation would give the attacker SYSTEM-level control of the affected host (CVSS 3.1: 7.8, High). The attacker needs a valid low-privileged local account and no user interaction, so this is a post-compromise escalation rather than an internet-facing entry point.

Affected

• Windows 10 Version 1607 (builds before 10.0.14393.9612)
• Windows 10 Version 1809 (builds before 10.0.17763.9376)
• Windows 10 Version 21H2 (builds before 10.0.19044.7807)
• Windows 10 Version 22H2 (builds before 10.0.19045.7807)
• Windows 11 Versions 23H2, 24H2, 25H2 and 26H2 (builds before the fixed builds listed by Microsoft)
• Windows 11 Version 26H1 (builds before 10.0.28000.3231)
• Windows Server 2012 and 2012 R2, including Server Core installations (builds before 6.2.9200.26434 and 6.3.9600.23470)
• Windows Server 2016 (builds before 10.0.14393.9612)

Fixed in

• Windows 10 Version 1607: 10.0.14393.9612
• Windows 10 Version 1809: 10.0.17763.9376
• Windows 10 Version 21H2: 10.0.19044.7807
• Windows 10 Version 22H2: 10.0.19045.7807 (verify against the MSRC table, as sources conflict)
• Windows Server 2016: 10.0.14393.9612
• Windows Server 2012 and 2012 R2: see the MSRC table for the fixed builds
• Fixes are included in the October 2026 cumulative updates from Microsoft. The KB number for each build is not confirmed here.

Workaround

Unknown. Microsoft does not describe a workaround; patching is the stated remedy.

• Third-party suggestion (not confirmed by Microsoft): disable the UPnP Device Host service (UPnPHost) on systems that do not need UPnP device discovery or control.

Exploitation

• Microsoft: not publicly disclosed, not exploited, exploitation rated as less likely.
• CISA SSVC: exploitation none, automatable no, technical impact total.
• Not listed in CISA KEV. EPSS is below 1%.
• No public proof of concept or confirmed in-the-wild exploitation was found at the time of research.
• Some third-party sources classify the flaw as CWE-120 instead of CWE-122.

Our recommendation

• Install the October 2026 cumulative update on all affected Windows clients and servers, and prioritise multi-user systems, terminal or RDS servers and any Windows 10 1607 host still in use.
• Confirm whether Windows 10 1607 is still serviced for your systems, or only under Extended Security Updates, and plan an upgrade or replacement if it is not.
• Disable the UPnP Device Host service on systems where UPnP is not required.
• Monitor for unexpected privilege changes and new SYSTEM-level processes on endpoints.

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

• Microsoft Security Update Guide: CVE-2026-85373 msrc.microsoft.com
• SentinelOne vulnerability database: CVE-2026-85373 www.sentinelone.com
• Vulners: CVE-2026-85373 vulners.com
• OpenCVE: CVE-2026-85373 app.opencve.io
• Strix: CVE-2026-85373 www.strix.ai
• VulDB: vuln 419193 vuldb.com

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, 02:12.