Microsoft Windows Win32k: Use-after-free leads to local privilege escalation

Summary

A use-after-free flaw in the Win32k kernel-mode graphics subsystem of Microsoft Windows allows an authorized local user to elevate privileges. An attacker with a low-privileged local account could gain SYSTEM rights, which would give full control over the affected host. Remote exploitation is not possible without a prior local logon.

Affected

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

Fixed in

• Windows 10 1809 and Windows Server 2019: 10.0.17763.9376 or later (the KB number is not yet verified; see the MSRC advisory)
• Windows 10 21H2: 10.0.19044.7807 or later
• Windows 10 22H2: 10.0.19045.7807 or later (unverified, one source gives a conflicting build)
• Windows 11 23H2: 10.0.22631.7652 or later
• Windows 11 24H2 and 25H2: 10.0.26100.9711 and 10.0.26200.9711 or later
• Windows 11 26H1: 10.0.28000.3231 or later
• Windows 11 26H2: 10.0.26300.9711 or later
• Windows Server 2022: 10.0.20348.5761 or later
• Windows Server 2025: 10.0.26100.33650 or later

Workaround

Unknown. No interim mitigation was found in the available sources. Check the MSRC advisory.

Exploitation

• No evidence of exploitation in the wild was found in the research.
• No public proof-of-concept was found.
• CISA KEV catalog status was not checked.
• EPSS was 0.00361 as of 16 Oct 2026 (low).
• CVSS 3.1 vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H (7.8, HIGH).

Our recommendation

• Install the October 2026 security update on all Windows hosts listed above, starting with multi-user systems, terminal servers and file servers.
• Verify the fixed build and KB number in the MSRC advisory before deployment.
• Until patched, restrict local interactive logons on shared hosts and enforce least privilege.
• Check whether Windows 10 1809 and Server 2019 are still supported in your fleet.
• Check the CISA KEV catalog and monitor for exploitation indicators.

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-2026-83762 msrc.microsoft.com
• Vulners: CVELIST CVE-2026-83762 (CNA data) vulners.com
• Vulners: NVD CVE-2026-83762 (EPSS) vulners.com
• SonicWall: Microsoft security bulletin coverage October 2026 www.sonicwall.com
• Strix AI: CVE-2026-83762 (conflicting 22H2 build) www.strix.ai
• OpenCVE: CVE-2026-83762 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, 03:08.