Microsoft Windows: Heap-based buffer overflow enables local privilege escalation

Summary

A heap-based buffer overflow (CWE-122) in Windows Servicing Stack Updates allows an authorized local attacker to elevate privileges. The CNA record lists Windows 10 versions 1607, 1809, 21H2 and 22H2, Windows 11 versions 23H2 to 26H2, and Windows Server 2012, 2012 R2 and 2016 as affected. An attacker needs local access with low privileges, for example a standard user account or malware already running on the system, and no user interaction is required. Successful exploitation can lead to full compromise of confidentiality, integrity and availability on the affected host.

Affected

• Windows 10 Version 1607 (and Windows Server 2016): builds below 10.0.14393.9612
• Windows 10 Version 1809: builds below 10.0.17763.9376
• Windows 10 Version 21H2: builds below 10.0.19044.7807
• Windows 10 Version 22H2: builds below 10.0.19045.7807
• Windows 11 Version 23H2: builds below 10.0.22631.7652
• Windows 11 Version 24H2 and 25H2: builds below 10.0.26100.9711 and 10.0.26200.9711
• Windows 11 Version 26H1: builds below 10.0.28000.3231
• Windows 11 Version 26H2: builds below 10.0.26300.9711
• Windows Server 2012 and 2012 R2: builds below 6.2.9200.26434 and 6.3.9600.23470

Fixed in

• Windows 10 Version 1607 and Windows Server 2016: 10.0.14393.9612 or later
• Other products: see the fixed builds in the MSRC advisory, as the CNA ranges above are the authoritative source
• Install the latest Servicing Stack Update and current Windows security updates

Workaround

Unknown.

• No vendor workaround was identified.

Exploitation

• CISA SSVC: exploitation none, not automatable, technical impact total.
• Not listed in CISA KEV.
• EPSS below 1 percent (secondary source).
• No public proof of concept was found; this does not prove that none exists.

Our recommendation

• Identify all Windows systems in scope, including Windows 10 1607 and Server 2016 hosts, and compare their builds with the affected ranges.
• Install the Servicing Stack Update and the current monthly Windows security updates as soon as possible, without waiting for the regular cycle to end.
• Verify the end-of-support date for Windows 10 1607 on Microsoft's lifecycle page; if these systems are still in use, plan replacement or isolation.
• Restrict local logon and limit standard user rights, and monitor for unexpected SYSTEM-level processes.

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-2026-83863 msrc.microsoft.com
• Vulners: CVE List record (CNA data) vulners.com
• Vulners: NVD record vulners.com
• OpenCVE: CVE-2026-83863 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, 02:46.