Microsoft Windows TCP/IP: Use-after-free allows local privilege escalation
Summary
A use-after-free flaw (CWE-416) in the Windows TCP/IP network stack affects several supported and older Windows 10, Windows 11 and Windows Server versions. An attacker who already has local access with low privileges, for example a logged-in user or a malicious process, can elevate privileges to full control of the host. The flaw is not directly reachable from the internet, and CISA SSVC lists exploitation as none.
Affected
- Windows 10 Version 1607: 10.0.14393.0 to before 10.0.14393.9612
- Windows 10 Version 1809: 10.0.17763.0 to before 10.0.17763.9376
- Windows 10 Version 21H2: 10.0.19044.0 to before 10.0.19044.7807
- Windows 10 Version 22H2: 10.0.19045.0 to before 10.0.19045.7807
- Windows 11 Version 23H2: 10.0.22631.0 to before 10.0.22631.7652
- Windows 11 Version 24H2: 10.0.26100.0 to before 10.0.26100.9711
- Windows 11 Version 25H2: 10.0.26200.0 to before 10.0.26200.9711
- Windows 11 Version 26H1: 10.0.28000.0 to before 10.0.28000.3231
- Windows 11 Version 26H2: 10.0.26300.0 to before 10.0.26300.9711
- Windows Server 2012 (including Server Core): 6.2.9200.0 to before 6.2.9200.26434
- Windows Server 2012 R2 (including Server Core): 6.3.9600.0 to before 6.3.9600.23470
- Windows Server 2016: 10.0.14393.0 to before 10.0.14393.9612
Fixed in
- Install the October 2026 cumulative update from Microsoft for your version. Fixed builds are the versions listed under affected, or higher.
- Windows 10 Version 1809 / Server 2019: KB5126651 (according to Tenable Nessus).
- Windows Server 2025: October 2026 security update KB5126646 (according to Tenable Nessus).
- Windows 10 Version 1607: KB number not confirmed. Check the MSRC page or the Microsoft Update Catalog.
Workaround
Unknown. No vendor or third-party workaround was identified. Installing the patch is the only known remediation.
Exploitation
- Not known to be exploited in the wild. CISA SSVC lists exploitation as none, and the CISA KEV status was not verified.
- EPSS score 0.0027 (very low).
- No public proof-of-concept found in the searches performed. This is not a complete check.
Our recommendation
- Identify all Windows 10 1607, Windows Server 2012 and 2016 systems and check whether they are still supported by Microsoft.
- Install the October 2026 cumulative update on all affected systems in the normal patch cycle, then reboot so the updated TCP/IP stack is active.
- Prioritise multi-user terminal servers and shared workstations, where low-privileged users can already run code.
- Monitor for exploitation and public proof-of-concept code, and review the MSRC page for updates.
Information from Microsoft (Patch Tuesday October 2026)
- Severity (Microsoft)
- Important
- Impact
- Elevation of privilege – Windows TCP/IP
- 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 Response Center: CVE-2026-70164 msrc.microsoft.com
- Strix: CVE-2026-70164 (mirror of CNA data) www.strix.ai
- Vulners: NVD record CVE-2026-70164 vulners.com
- Vulners: MSCVE MS:CVE-2026-70164 vulners.com
- OpenCVE: CVE-2026-70164 app.opencve.io
- VulDB: entry 418609 vuldb.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, 09:06.
Original description (NVD)
Use after free in Windows TCP/IP 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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