Microsoft Windows: Local privilege escalation via use-after-free in NTFS
Summary
A use-after-free flaw (CWE-416) in the Windows NTFS file system driver allows an attacker with local access and a low-privilege account to elevate privileges. Successful exploitation can lead to full control of the system, with high impact on confidentiality, integrity and availability. The attack is not reachable over the network and requires a valid local account, so the main risk lies on shared servers, terminal servers and multi-user PCs.
Affected
- Windows 10 Version 1607 (builds before 10.0.14393.9612)
- Windows 10 Version 1809 (builds before 10.0.17763.9376)
- Windows 10 Version 21H2 (builds before 10.0.19044.7807)
- Windows 10 Version 22H2 (builds before 10.0.19045.7807)
- Windows 11 Version 23H2 (builds before 10.0.22631.7652)
- Windows 11 Version 24H2 (builds before 10.0.26100.9711)
- Windows 11 Version 25H2 (builds before 10.0.26200.9711)
- Windows 11 Version 26H1 (builds before 10.0.28000.3231)
- Windows 11 Version 26H2 (builds before 10.0.26300.9711)
- Windows Server 2012 R2 incl. Server Core (builds before 6.3.9600.23470)
- Windows Server 2016 incl. Server Core (builds before 10.0.14393.9612)
- Windows Server 2019 (builds before 10.0.17763.9376)
Fixed in
- Install the October 2026 cumulative security update for your build, which contains the fixed builds listed above.
- Confirm the exact KB number for each build in the Microsoft Security Update Guide. Third-party listings are inconsistent, for example for Windows 10 22H2.
Workaround
- No vendor-documented workaround. Install the update.
- Compensating controls (not vendor guidance): restrict local logon on shared servers and terminal servers, limit standard accounts on multi-user hosts, and monitor for unexpected privilege changes.
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 0.00353 (very low).
- No public proof of concept found in searches; this is not conclusive.
Our recommendation
- Install the October 2026 cumulative update on all affected Windows 10, Windows 11 and Windows Server systems, starting with multi-user servers, terminal servers and file servers.
- Check the support status of Windows 10 1607, Windows Server 2016, Windows 10 1809 and Windows Server 2019. If no updates are available, plan replacement or Extended Security Updates.
- Until patched, limit local logon and standard accounts on shared hosts and monitor for unexpected privilege changes.
Information from Microsoft (Patch Tuesday October 2026)
- Severity (Microsoft)
- Important
- Impact
- Elevation of privilege – Windows NTFS
- Status on Patch Tuesday
- Neither exploited nor publicly disclosed
- Exploitability assessment
- Exploitation less likely
- 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-2026-83859 msrc.microsoft.com
- NVD mirror (Vulners): CVE-2026-83859 vulners.com
- OpenCVE: CVE-2026-83859 app.opencve.io
- CNA version data (Vulners): CVE-2026-83859 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, 02:48.
Original description (NVD)
Use after free in Windows NTFS 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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