Microsoft Windows Kernel: Use-after-free allows local privilege escalation
Summary
A use-after-free flaw in the Windows kernel allows an authorized local user to elevate privileges to the highest level on the system. An attacker needs an existing low-privileged foothold, such as a phished user account or malware on a workstation. There is no network attack vector, and CISA lists no known exploitation at the time of research.
Affected
- Windows 11 version 23H2: builds below 10.0.22631.7652
- Windows 11 version 24H2: builds below 10.0.26100.9711
- Windows 11 version 25H2: builds below 10.0.26200.9711
- Windows 11 version 26H2: builds below 10.0.26300.9711
- Windows Server 2025 (including Server Core): builds below 10.0.26100.33650
Fixed in
- Windows 11 23H2: cumulative update KB5126653 (October 2026); the exact fixed build must be confirmed on the KB support page, as sources disagree (22631.7652 or 22621.7652)
- Windows 11 24H2, 25H2, 26H2: cumulative update KB5127648 (October 2026), builds 10.0.26100.9711, 10.0.26200.9711, 10.0.26300.9711
- Windows Server 2025: fixed at build 10.0.26100.33650
Workaround
Unknown. No vendor-published workaround was found; installing the update is the remedy.
Exploitation
- Not listed in CISA KEV at the time of research.
- CISA SSVC data: exploitation none, automatable no, technical impact total.
- No public proof of concept confirmed for this CVE.
Our recommendation
- Install the October 2026 cumulative update on all affected Windows 11 and Server 2025 systems, prioritising shared, multi-user, terminal server and admin workstations.
- Plan the upgrade of systems still on Windows 11 23H2 before 10 Nov 2026, the end of servicing, as they will not receive further fixes afterwards.
- Verify the installed build after patching and monitor for suspicious privilege escalation on endpoints.
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-2026-83796 msrc.microsoft.com
- OpenCVE: CVE-2026-83796 app.opencve.io
- NVD via Vulners: CVE-2026-83796 vulners.com
- Microsoft Message Center MC1506288 mc.merill.net
- BleepingComputer: KB5127648 and KB5126653 released www.bleepingcomputer.com
- Wikipedia: Windows 11 version history en.wikipedia.org
- VulDB: CVE-2026-83796 vuldb.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, 02:58.
Original description (NVD)
Use after free in Windows Kernel 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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