Microsoft Windows 10 1809: Elevation of privilege in Win32 Kernel Subsystem
Summary
A use-after-free flaw (CWE-416) in the Windows Win32 Kernel Subsystem of Windows 10 version 1809 and Windows Server 2019 allows an authenticated local user to elevate privileges. An attacker needs an existing low-privilege session on the machine; the flaw cannot be exploited remotely. Successful exploitation could give full control over the system. CISA's automated assessment records no known exploitation, and no public proof of concept was found.
Affected
- Windows 10 Version 1809 (builds 10.0.17763.0 to below 10.0.17763.9376, according to the CVE record; build to be verified in the MSRC table)
- Windows Server 2019 and Server Core installation (same build range)
- Further Windows 10 and Windows 11 versions and Windows Server 2022 and 2025 are listed in the official record.
Fixed in
- Security update from October 2026 (Microsoft advisory; reported as KB5126651 for Windows 10 1809 and Server 2019, to be confirmed on the MSRC page)
Workaround
- Unknown. No vendor-documented workaround was found. Patching is the expected fix.
Exploitation
- Not listed in CISA KEV.
- CISA SSVC (automated): Exploitation none, Automatable no, Technical Impact total.
- EPSS score: 0.27%.
- No public proof of concept found.
- Exploitation requires local access and a low-privilege account.
Our recommendation
- Install the October 2026 cumulative update for Windows 10 1809 and Server 2019 in the next patch cycle, prioritising multi-user systems, terminal servers and RDS hosts.
- Confirm installation with a patch-management report.
- Limit local logons to trusted users and restrict local accounts.
- Keep endpoint protection active and monitor for privilege-escalation activity.
- Verify the Windows edition and end-of-support date of each device before planning upgrades.
Information from Microsoft (Patch Tuesday October 2026)
- Severity (Microsoft)
- Important
- Impact
- Elevation of privilege – Windows Win32 Kernel Subsystem
- Status on Patch Tuesday
- Neither exploited nor publicly disclosed
- Exploitability assessment
- Exploitation unlikely
- Product family
- Windows, Windows ESU (Extended Security Updates)
- Updates (KB)
- KB5126651, KB5126655, KB5126657, KB5126646, KB5127648, KB5126653
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Microsoft Security Update Guide: CVE-2026-83901 msrc.microsoft.com
- OpenCVE: CVE-2026-83901 app.opencve.io
- Vulners NVD record: CVE-2026-83901 vulners.com
- Vulners MSCVE record: MS:CVE-2026-83901 vulners.com
- EPSS discussion (GitHub): CVE-2026-83901 github.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 4 Nov 2026, 08:02.
Original description (NVD)
Use after free in Windows Win32 Kernel Subsystem allows an authorized attacker to elevate privileges locally.
NVD references (1)
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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