Windows Hyper-V: Use after free allows local privilege escalation
Summary
A use-after-free flaw in Microsoft Windows Hyper-V allows an authorized local attacker to elevate privileges. The attacker needs an existing local foothold with low privileges, so the flaw is a step in an attack chain rather than a direct entry point. The CVSS score is 7.8 (High), with high impact on confidentiality, integrity and availability.
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
Fixed in
- Windows 11 24H2, 25H2, 26H2: October 13, 2026 cumulative update (reported as KB5127648, builds 10.0.26100.9711, 10.0.26200.9711, 10.0.26300.9711)
- Windows 11 26H1: build 10.0.28000.3231 or later (reported as KB5127646)
- Windows Server 2025: build 10.0.26100.33650 or later (reported as KB5126646)
- KB mapping is not yet confirmed by the vendor page; verify on MSRC.
Workaround
Unknown.
Exploitation
- Not known to be exploited.
- CISA SSVC: exploitation none, automatable no.
- No public proof of concept found at time of research.
- Not listed in CISA KEV at time of research.
Our recommendation
- Install the October 2026 cumulative update on all affected Windows 11 and Windows Server 2025 systems and confirm the build numbers.
- Verify the affected and fixed build ranges and KB mapping on the MSRC advisory.
- Identify systems with the Hyper-V feature enabled, especially Windows Server 2025 virtualization hosts, and prioritise them.
- Plan the upgrade of Windows 11 24H2 Home and Pro devices, whose support ends with this update.
- Monitor for public proof of concept code or KEV listing changes.
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 Response Center advisory CVE-2026-96223 msrc.microsoft.com
- OpenCVE CVE-2026-96223 app.opencve.io
- Vulners CVE list entry CVE-2026-96223 vulners.com
- VulDB CVE-2026-96223 vuldb.com
- Strix CVE-2026-96223 (third-party build ranges) www.strix.ai
- EUVD-2026-100371 (conflicting description) vulners.com
- NinjaOne KB5127648 catalog entry www.ninjaone.com
- Notebookcheck: KB5127648 update and Windows 11 24H2 Home/Pro end of support www.notebookcheck.net
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, 00:58.
Original description (NVD)
Use after free in Windows Hyper-V 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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