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

Summary

A heap-based buffer overflow in the Windows Kernel allows an authorized local attacker to elevate privileges. The attacker needs an existing low-privilege foothold on the system, for example through a user account, an insider or a phishing payload that runs code first. The impact is rated total for confidentiality, integrity and availability (CVSS 3.1: 7.8).

Affected

• Windows 10 Version 1809 and Windows Server 2019 (including Server Core): builds 10.0.17763.0 to before 10.0.17763.9376
• Windows 10 Version 21H2: builds 10.0.19044.0 to before 10.0.19044.7807
• Windows 10 Version 22H2: builds 10.0.19045.0 to before 10.0.19045.7807
• Windows 11 Version 23H2: builds 10.0.22631.0 to before 10.0.22631.7652
• Windows 11 Version 24H2: builds 10.0.26100.0 to before 10.0.26100.9711
• Windows 11 Version 25H2: builds 10.0.26200.0 to before 10.0.26200.9711
• Windows 11 Version 26H1: builds 10.0.28000.0 to before 10.0.28000.3231
• Windows 11 Version 26H2: builds 10.0.26300.0 to before 10.0.26300.9711
• Windows Server 2022: builds 10.0.20348.0 to before 10.0.20348.5761
• Windows Server 2025 (including Server Core): builds 10.0.26100.0 to before 10.0.26100.33650

Fixed in

• Windows 10 1809 and Server 2019: 10.0.17763.9376 (update KB5126651)
• Windows 10 21H2: 10.0.19044.7807
• Windows 10 22H2: 10.0.19045.7807
• Windows 11 23H2: 10.0.22631.7652
• Windows 11 24H2 and 25H2: 10.0.26100.9711 and 10.0.26200.9711
• Windows 11 26H1: 10.0.28000.3231
• Windows 11 26H2: 10.0.26300.9711
• Windows Server 2022: 10.0.20348.5761
• Windows Server 2025: 10.0.26100.33650

Verify the exact versions on the Microsoft Security Update Guide.

Workaround

Unknown. No vendor or third-party workaround has been identified. Patching is the fix.

Exploitation

• Not known to be exploited in the wild.
• Not listed in the CISA KEV catalog.
• CISA SSVC: Exploitation none, automatable no, technical impact total.
• EPSS about 0.36 percent.
• No public proof of concept found.

Our recommendation

• Install the October 2026 cumulative update for each affected Windows branch as part of the normal patch cycle, and do not postpone it.
• Prioritise systems that are still on Windows 10 1809 or other unsupported editions, and check their support status.
• Restrict local logon and limit accounts with local access on servers and shared workstations.
• Monitor for unusual privilege changes and suspicious local 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-2026-83768 msrc.microsoft.com
• Vulners NVD record: CVE-2026-83768 vulners.com
• Strix CVE record: CVE-2026-83768 www.strix.ai
• Tenable plugin 365475 (KB5126651) www.tenable.com
• Miggo vulnerability database: CVE-2026-83768 www.miggo.io
• OpenCVE: CVE-2026-83768 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, 03:03.