Windows 10 Version 1607: Use after free in LSASS enables privilege escalation
Summary
A use-after-free vulnerability in the Windows Local Security Authority Subsystem Service (LSASS) on Windows 10 Version 1607 and Windows Server 2016 allows an authorized local attacker to elevate privileges. The attacker needs a low-privileged local account and must already be able to run code on the system. Microsoft fixed the issue in its October 2026 security update. CVSS 7.8 (High).
Affected
- Windows 10 Version 1607 (10.0.14393.0 to below 10.0.14393.9612)
- Windows Server 2016 and Server Core installation (10.0.14393.0 to below 10.0.14393.9612)
- Other Windows 10, Windows 11 and Windows Server 2019/2022 builds are listed in the CNA record.
Fixed in
- Windows 10 Version 1607 and Windows Server 2016: build 10.0.14393.9612 or later
- Delivered with the October 2026 Microsoft security update
- Unknown: specific KB number for Windows 10 1607; confirm the build on the MSRC page before rollout
Workaround
- No vendor workaround known; apply the update.
- General hardening (not from the sources): enable LSA protection and Credential Guard where supported, enforce least privilege, run EDR.
Exploitation
- Not listed in CISA KEV.
- CISA SSVC: exploitation none, not automatable, total technical impact.
- EPSS about 0.3% (0.00341 per Vulnrichment; Rapid7 shows N/A).
- No public proof of concept found in searches; this does not prove none exists.
Our recommendation
- Patch Windows 10 1607 and Windows Server 2016 to build 10.0.14393.9612 or later with the October 2026 update.
- Inventory systems running these versions and prioritise servers and admin workstations.
- Enable LSA protection and Credential Guard where supported.
- Monitor for unusual privilege changes and new local administrator accounts.
Information from Microsoft (Patch Tuesday October 2026)
- Severity (Microsoft)
- Important
- Impact
- Elevation of privilege – Windows Local Security Authority Subsystem Service (LSASS)
- 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-2026-70015 msrc.microsoft.com
- VulnCheck/CVE List record (CVELIST) vulners.com
- NVD record (NVD) vulners.com
- Microsoft MSRC record (MS) vulners.com
- OpenCVE entry app.opencve.io
- Rapid7 vulnerability database entry www.rapid7.com
- GovCERT.HK alert www.govcert.gov.hk
- Vulnrichment record (EPSS and SSVC) 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, 04:33.
Original description (NVD)
Use after free in Windows Local Security Authority Subsystem Service (LSASS) 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.
Affected? We can help.
We check whether your systems are affected, install updates and close the gap – continuously with the System Health Checker if you wish.