Microsoft Windows: Use-after-free in Win32 kernel subsystem allows local privilege escalation
Summary
A use-after-free flaw in the Windows Win32 kernel subsystem (win32k) allows an authorized local user to elevate privileges to a higher level, including SYSTEM. The attacker needs an existing low-privilege account or code running on the system. Microsoft rates the vulnerability as Important with CVSS 7.8, and it is not remotely exploitable.
Affected
- 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 2025 (including Server Core): 10.0.26100.0 to before 10.0.26100.33650
- Windows 10 and older Windows Server versions: Unknown.
Fixed in
- Windows 11 24H2: build 10.0.26100.9711 or later
- Windows 11 25H2: build 10.0.26200.9711 or later
- Windows 11 26H1: build 10.0.28000.3231 or later
- Windows 11 26H2: build 10.0.26300.9711 or later
- Windows Server 2025: build 10.0.26100.33650 or later
- Microsoft released the fixes on 13 October 2026. Per-version cumulative update KB numbers: check the MSRC advisory.
Workaround
Unknown. No workaround has been identified; apply the Microsoft security update.
Exploitation
- Exploited in the wild: Unknown. No CISA KEV entry.
- Public proof of concept: None known; Microsoft rates exploit code maturity as Unproven.
- CISA SSVC: Exploitation none, Automatable no, Technical impact total.
- EPSS: 0.00318.
Our recommendation
- Install the October 2026 Windows security update on all affected systems, prioritising Remote Desktop/terminal servers and shared workstations with many local users.
- Check the MSRC advisory for the exact KB number for each Windows version.
- Restrict local logon and remote sessions to required accounts and keep endpoint protection active.
- Monitor for unusual privilege changes or new SYSTEM processes.
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-2026-96249 msrc.microsoft.com
- Vulners CVE record vulners.com
- VulDB CVE entry vuldb.com
- OpenCVE CVE entry app.opencve.io
- Vulnrichment record 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, 00:56.
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.
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