Windows 10 1607: Use-after-free in Win32k allows local privilege escalation
Summary
A use-after-free flaw in the Win32k kernel subsystem of Windows 10 Version 1607 and Windows Server 2016 allows an authorized local user to elevate privileges. An attacker who already has a low-privileged account on the system can gain higher privileges, which the CVSS vector rates as high impact to confidentiality, integrity and availability. The attack requires high complexity and local access.
Affected
- Windows 10 Version 1607 before build 10.0.14393.0 to < 10.0.14393.9612
- Windows Server 2016 before build 10.0.14393.9612
- The CNA record also lists other Windows 10 and Windows 11 versions and Windows Server 2012 and 2012 R2 builds (see MSRC)
Fixed in
- Windows 10 Version 1607 and Windows Server 2016: build 10.0.14393.9612 or later (associated with the October 2026 update KB5126868 according to Microsoft release-health pages; verify against MSRC)
Workaround
Unknown. No vendor workaround identified. Windows 10 1607 (LTSB 2016) is out of standard updates; the paid Extended Security Updates (ESU) program is the only route to patches.
Exploitation
- CISA SSVC: exploitation none, not automatable, total technical impact
- No public proof of concept or in-the-wild exploitation found at the time of research
Our recommendation
- Verify the fixed build against the MSRC advisory before rollout
- Identify all Windows 10 1607 and Server 2016 systems and restrict local logon to trusted users
- Plan migration off Windows 10 1607 or enrol devices in paid ESU, since standard security updates have ended
- Monitor for privilege escalation indicators on affected systems
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 more likely
- Product family
- Windows, Windows ESU (Extended Security Updates)
- Updates (KB)
- KB5127648, KB5126651, KB5126655, KB5126657, KB5126646, KB5126653
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Microsoft Security Update Guide: CVE-2026-70236 msrc.microsoft.com
- Microsoft: Windows 10 1607 and Windows Server 2016 release health status learn.microsoft.com
- Microsoft: Windows release information learn.microsoft.com
- NVD mirror (vulners): CVE-2026-70236 vulners.com
- 4sysops: Windows 10 Enterprise LTSB 2016 end of support and ESU 4sysops.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, 08:58.
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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