Microsoft Windows Win32k: Local privilege escalation via use after free
Summary
A use-after-free flaw in the Win32k kernel subsystem of Windows 11 and Windows Server 2025 allows an attacker with a local, authorized account to elevate privileges. Successful exploitation can give the attacker SYSTEM rights, with high impact on confidentiality, integrity and availability. The attack requires local access and high attack complexity, and it is not reachable from the internet.
Affected
- Windows 11 version 23H2: builds before 10.0.22631.7652
- Windows 11 version 24H2: builds before 10.0.26100.9711
- Windows 11 version 25H2: builds before 10.0.26200.9711
- Windows 11 version 26H1: builds before 10.0.28000.3231
- Windows 11 version 26H2: builds before 10.0.26300.9711
- Windows Server 2025 (including Server Core): builds before 10.0.26100.33650
Fixed in
- Windows 11 23H2: 10.0.22631.7652 (October 2026 cumulative update, Tenable reference KB5126653)
- Windows 11 24H2: 10.0.26100.9711
- Windows 11 25H2: 10.0.26200.9711
- Windows 11 26H1: 10.0.28000.3231
- Windows 11 26H2: 10.0.26300.9711
- Windows Server 2025: 10.0.26100.33650 (Tenable reference KB5126646)
Workaround
Unknown.
Exploitation
- CISA SSVC: exploitation none, automatable no, technical impact total
- Not listed in CISA KEV; EPSS below 1% (per OpenCVE)
- No public proof of concept found at the time of research
Our recommendation
- Install the October 2026 cumulative update on all affected Windows 11 and Windows Server 2025 systems, and restart afterwards so the new kernel code is loaded
- Prioritise systems with many local users, shared terminal or file servers, and workstations exposed to phishing
- Plan the upgrade of Windows 11 23H2 systems to 24H2 or 25H2 and verify the end-of-servicing date on Microsoft's lifecycle page
- Monitor for public exploit code and for changes in the CISA KEV catalog
Information from Microsoft (Patch Tuesday October 2026)
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Microsoft Security Update Guide: CVE-2026-70144 msrc.microsoft.com
- Vulners CVE record CVE-2026-70144 vulners.com
- Vulners CVELIST record CVE-2026-70144 vulners.com
- OpenCVE CVE-2026-70144 app.opencve.io
- Tenable plugin 365473 (KB5126646) www.tenable.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, 09:12.
Original description (NVD)
Use after free in Windows Win32 Kernel Subsystem 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.