Windows Win32k: Heap-based buffer overflow enables local privilege escalation
Summary
A heap-based buffer overflow in the Windows Win32k kernel component allows an authorized local attacker to elevate privileges. Successful exploitation gives the attacker higher privileges on the affected system and, if chained with malware or phishing, potentially full control of the endpoint. The attacker needs local access and low privileges; the flaw cannot be exploited remotely.
Affected
- Windows 11 Version 23H2 (10.0.22631.0 to before 10.0.22631.7652)
- 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 2022 (10.0.20348.0 to before 10.0.20348.5761)
- Windows Server 2025 incl. Server Core installation (10.0.26100.0 to before 10.0.26100.33650)
Fixed in
- Windows 11 23H2: 10.0.22631.7652 or later (October 2026 update; KB5126653 according to a Tenable listing, not verified against MSRC)
- Other editions: build numbers as listed under affected, or later; confirm exact builds in the MSRC advisory.
Workaround
Unknown. No vendor workaround has been published; patching is the fix. Until patched, limit local administrator rights and enforce least privilege.
Exploitation
- CISA SSVC: Exploitation none, Automatable no, Technical Impact total.
- EPSS 0.00361 (low).
- No public proof of concept or exploit code found.
- A GitHub issue from 27 Oct 2026 describes a similar heap overflow but does not name this CVE.
Our recommendation
- Deploy the October 2026 cumulative update to all Windows 11 and Windows Server endpoints in the regular patch cycle.
- Check that devices run a supported Windows edition; Windows 11 23H2 Home and Pro may no longer receive fixes.
- Limit local administrator rights and monitor endpoints for privilege escalation activity.
- No emergency action needed unless exploitation is reported.
Information from Microsoft (Patch Tuesday October 2026)
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- MSRC Security Update Guide: CVE-2026-83757 msrc.microsoft.com
- NVD record via Vulners vulners.com
- CNA record via Vulners vulners.com
- OpenCVE entry app.opencve.io
- Strix CVE entry (build data, unverified) www.strix.ai
- GitHub issue (related, does not name this CVE) github.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, 03:06.
Original description (NVD)
Heap-based buffer overflow in Windows Win32K 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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