Microsoft Windows Win32k: Use-after-free leads to local privilege escalation
Summary
A use-after-free flaw in the Windows Win32k kernel subsystem allows an authorized local attacker to elevate privileges. The attacker needs local code execution or an authenticated local session, and the attack complexity is high. Successful exploitation would give full control over confidentiality, integrity and availability of the affected system.
Affected
- Windows 11 Version 24H2 (10.0.26100.0 before 10.0.26100.9711)
- Windows 11 Version 25H2 (10.0.26200.0 before 10.0.26200.9711)
- Windows 11 Version 26H1 (10.0.28000.0 before 10.0.28000.3231)
- Windows 11 Version 26H2 (10.0.26300.0 before 10.0.26300.9711)
- Windows Server 2025, including Server Core (10.0.26100.0 before 10.0.26100.33650)
Fixed in
- Install the October 2026 security update for each affected version.
- Fixed build for Windows 11 24H2: unconfirmed; the sources conflict (9711 vs. 33650). Verify in the MSRC advisory.
- KB number for Windows 11 24H2: Unknown.
Workaround
- No vendor workaround known.
- Restrict local user privileges according to least-privilege principles until the update is installed (generic measure, not a Microsoft mitigation).
Exploitation
- Not listed in CISA KEV.
- CISA SSVC: exploitation none, automatable no, technical impact total.
- Microsoft temporal vector E:U/RL:O/RC:C: exploit code maturity unproven, report confirmed.
- No public proof of concept or in-the-wild exploitation found. Status unconfirmed; monitor.
Our recommendation
- Patch all affected Windows 11 and Windows Server 2025 systems with the October 2026 cumulative update in the normal cycle, without deferral.
- Prioritise multi-user systems such as terminal servers (RDS), shared workstations and file or print servers.
- Verify the fixed build for 24H2 in the MSRC advisory before rollout.
- Monitor for exploitation indicators and re-check CISA KEV and public exploit sources.
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-2026-70076 msrc.microsoft.com
- Microsoft Security Update Guide (en-US) msrc.microsoft.com
- OpenCVE: CVE-2026-70076 app.opencve.io
- Vulners NVD: CVE-2026-70076 vulners.com
- SonicWall: Microsoft security bulletin coverage for October 2026 www.sonicwall.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, 09:16.
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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