Windows 10 1607: Use after free in Local Security Authority Server
Summary
A use-after-free flaw in the Local Security Authority Server (lsasrv) of Windows 10 Version 1607 allows an authorized local attacker to elevate privileges. Exploitation requires a low-privileged local account and a high attack complexity. Successful exploitation can lead to full control of the affected system.
Affected
- Windows 10 Version 1607 (x86 and x64): builds below 10.0.14393.9612
- The CNA record also lists other Windows 10, Windows 11 and Windows Server versions (e.g. 1809, 21H2, 22H2, 2012, 2012 R2, 2016) with their own fixed builds
Fixed in
- Windows 10 Version 1607: OS Build 14393.9612 (October 2026 update, KB5126868) per Microsoft release health notes; not confirmed as the build named in the MSRC advisory, which could not be retrieved
Workaround
Unknown.
Exploitation
- CISA SSVC: exploitation none, automatable no, technical impact total
- EPSS about 0.002
- No public proof of concept or evidence of exploitation found; this is not a confirmed negative
Our recommendation
- Inventory all Windows 10 1607 devices and check for other affected builds
- Install the October 2026 cumulative update (build 14393.9612 or later) on 1607 systems that still receive updates, or enrol them in Extended Security Updates
- Plan migration off Windows 10 1607: it reached end of updates on October 13, 2026, so future vulnerabilities will not be fixed
- Monitor the MSRC update guide and CISA KEV for changes in exploitation status
Information from Microsoft (Patch Tuesday October 2026)
- Severity (Microsoft)
- Important
- Impact
- Elevation of privilege – Microsoft Local Security Authority Server (lsasrv)
- 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-2026-83722) msrc.microsoft.com
- NVD/CNA mirror: affected ranges vulners.com
- CVSS and SSVC data app.opencve.io
- NVD record and EPSS vulners.com
- Microsoft release health: Windows 10 1607 and Windows Server 2016 end of servicing learn.microsoft.com
- Windows 10 LTSB 2016 end of support and ESU options 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, 08:24.
Original description (NVD)
Use after free in Microsoft Local Security Authority Server (lsasrv) 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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