Windows Ancillary Function Driver: Privilege escalation via use after free
Summary
The Windows Ancillary Function Driver for WinSock in Windows 10 Version 1607 and Windows Server 2016 contains a use-after-free flaw (CWE-416). A local attacker with low privileges who wins a race condition can gain SYSTEM privileges, with high impact on confidentiality, integrity and availability. The vulnerability is not remotely exploitable and requires local code execution or a low-privilege account on the system. Microsoft reports no public disclosure and no known exploitation.
Affected
- Windows 10 Version 1607: 10.0.14393.0 to before 10.0.14393.9612
- Windows Server 2016: 10.0.14393.0 to before 10.0.14393.9612
- The CNA record also lists other Windows 10, Windows 11 and Windows Server 2012/2012 R2 builds.
Fixed in
- Windows 10 Version 1607 and Windows Server 2016: build 10.0.14393.9612 or later, included in Microsoft's October 2026 update (released 13 Oct 2026)
- KB article numbers: Unknown. Verify on the MSRC page before deployment.
Workaround
Unknown.
Exploitation
- Publicly disclosed: No
- Exploited: No
- Microsoft exploitability assessment: Exploitation Less Likely
- EPSS: 0.0027 (very low)
- No public proof of concept found in our searches (not exhaustively verified)
Our recommendation
- Install the October 2026 security update on all affected Windows 10 1607 and Windows Server 2016 systems, prioritising multi-user, shared, kiosk and production systems.
- Plan the upgrade of Windows 10 Version 1607 to a supported Windows version, and check Microsoft's lifecycle page for your edition.
- Until patched, restrict local logon to trusted users and isolate legacy systems where possible.
- Monitor for new proof-of-concept or exploitation reports and re-check this entry in 1 to 2 weeks.
Information from Microsoft (Patch Tuesday October 2026)
- Severity (Microsoft)
- Important
- Impact
- Elevation of privilege – Windows Ancillary Function Driver for WinSock
- 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-2026-70168 msrc.microsoft.com
- Vulners: CVE-2026-70168 (CVE list record) vulners.com
- Vulners: CVE-2026-70168 (NVD record, EPSS) vulners.com
- Strix: CVE-2026-70168 www.strix.ai
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 Ancillary Function Driver for WinSock 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.