Windows 10 1607: Use-after-free in Windows Installer allows privilege escalation
Summary
Windows Installer in Windows 10 Version 1607 contains a use-after-free flaw (CWE-416) that allows local privilege escalation. An authorized local user who can run a crafted installer or MSI package may gain higher privileges, potentially up to SYSTEM. The attack is not internet-facing and requires a local logon; the NVD CVSS 3.1 score is 7.0 (High).
Affected
- Windows 10 Version 1607 (builds 10.0.14393.0 up to, but not including, 10.0.14393.9612), including the LTSB 2016 editions
- The CNA record also lists Windows Server 2016 with the same build range; other Windows 10, Windows 11 and Windows Server 2012 / 2012 R2 builds are listed too but are outside this entry
Fixed in
- Build 10.0.14393.9612 or later, in the October 13, 2026 cumulative update KB5126868 (not confirmed that this update names CVE-2026-83718)
- Build 10.0.14393.9615 or later, in the out-of-band update KB5134123 (October 26, 2026), the newest 1607 build
Workaround
Unknown. No vendor workaround was found, and no alternative mitigation is documented in the sources.
Exploitation
- Not listed in the CISA KEV catalog
- CISA SSVC: exploitation none, automatable no, technical impact total
- EPSS about 0.0028 (very low)
- No public proof of concept or exploit found in the research; this means nothing was found, not that none exists
Our recommendation
- Identify all Windows 10 1607 and Windows Server 2016 hosts and install build 14393.9615 or later.
- Treat hosts that cannot be patched as high-risk: limit local logons and restrict who can run installers.
- Check the end-of-updates status of Windows 10 Enterprise LTSB 2016 (reached October 13, 2026) and plan a migration, because future security fixes may not be available.
Information from Microsoft (Patch Tuesday October 2026)
- Severity (Microsoft)
- Important
- Impact
- Elevation of privilege – Windows Installer
- Status on Patch Tuesday
- Neither exploited nor publicly disclosed
- Exploitability assessment
- Exploitation less 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-2026-83718 msrc.microsoft.com
- Vulners CVELIST record CVE-2026-83718 vulners.com
- OpenCVE CVE-2026-83718 app.opencve.io
- KB5126868: Windows 10 1607 security update (October 2026) support.microsoft.com
- KB5134123: Windows 10 1607 update (October 2026) support.microsoft.com
- Windows 10 1607 and Windows Server 2016 release health status learn.microsoft.com
- Windows release information learn.microsoft.com
- Vulners NVD record CVE-2026-83718 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 4 Nov 2026, 08:26.
Original description (NVD)
Use after free in Windows Installer 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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