Microsoft COM for Windows: Heap-based buffer overflow allows local privilege escalation

Summary

A heap-based buffer overflow in Microsoft COM for Windows allows an authorized local attacker to elevate privileges on the affected Windows system. The attacker needs an existing local account with low privileges and cannot exploit the flaw remotely from the internet. If exploited, the attacker could gain full control over the confidentiality, integrity and availability of the host.

Affected

• Windows 10 Version 1607 (Server 2016 also listed): builds 10.0.14393.0 to below 10.0.14393.9612
• Windows 10 Version 1809: builds below 10.0.17763.9376
• Windows 10 Version 21H2 and 22H2: builds below 10.0.19044.7807 and 10.0.19045.7807 (sources differ, verify in MSRC)
• Windows 11 Version 23H2, 24H2, 25H2, 26H1 and 26H2: various builds below the fixed versions listed by Microsoft
• Windows Server 2012 and 2012 R2: builds below 6.2.9200.26434 and 6.3.9600.23470
• Windows Server 2016: builds below 10.0.14393.9612
• Windows Server 2019, 2022 and 2025 are also listed in some sources; verify in the MSRC entry

Fixed in

• Install the Microsoft security update from October 13, 2026 for your Windows version, which contains the fixed builds listed in the MSRC entry.
• Windows 10 1607: build 10.0.14393.9612 or later.
• Windows 10 1809: build 10.0.17763.9376 or later.

Workaround

• Unknown. No vendor workaround is documented; installing the update is the remedy.

Exploitation

• CISA SSVC: exploitation none, automatable no, technical impact total.
• Not listed in the CISA KEV catalog.
• EPSS is low (about 0.3%).
• No public proof of concept found; no known exploitation in the wild.

Our recommendation

• Install the October 13, 2026 Windows security update on all affected systems and reboot afterwards.
• Prioritise shared PCs, terminal or RDS hosts and servers where users log on locally.
• Check whether any systems still run Windows 10 1607 and whether they are still supported; plan an upgrade if not.
• Restrict local logons and limit who can run code on multi-user systems until patched.
• Verify that each system reaches the fixed build listed in the MSRC Security Update Guide.

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-2026-69909 msrc.microsoft.com
• Microsoft Windows 10 1607 update KB5126868 support.microsoft.com
• NVD/Vulners listing of affected ranges vulners.com
• OpenCVE CVE-2026-69909 app.opencve.io
• Positive Technologies advisory PT-2026-112099 vulners.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, 04:44.