Microsoft Windows: Winlogon elevation of privilege via heap-based buffer overflow
Summary
A heap-based buffer overflow in the Windows Winlogon component allows a locally authenticated attacker with low privileges to elevate privileges. Successful exploitation can lead to full control of the system, including SYSTEM rights. The attacker needs an existing local user account, and the flaw cannot be exploited remotely.
Affected
- Windows 11 23H2 before 10.0.22631.7711
- Windows 11 24H2 before 10.0.26100.9974
- Windows 11 25H2 before 10.0.26200.9974
- Windows 11 26H1 before 10.0.28000.3501
- Windows 11 26H2 before 10.0.26300.9974
- Windows Server 2025 (including Server Core installation) before 10.0.26100.33822
Fixed in
- Install the November 2026 security update from Microsoft for the affected Windows versions listed above.
- Fixed builds according to the CVE record: 10.0.22631.7711 (23H2), 10.0.26100.9974 (24H2), 10.0.26200.9974 (25H2), 10.0.28000.3501 (26H1), 10.0.26300.9974 (26H2), 10.0.26100.33822 (Server 2025).
- The KB number has not been verified; check it on the MSRC page before deployment.
Workaround
Unknown. No vendor workaround is documented because a patch is available.
Exploitation
- Microsoft's CVSS vector marks exploit code maturity as Unproven (E:U), so no public exploit code was known at release.
- CISA SSVC: exploitation none, automatable no, technical impact total.
- A third-party report says one vulnerability from the November 2026 release was exploited in the wild. It is not confirmed that this CVE is that vulnerability.
Our recommendation
- Install the November 2026 security update on all affected Windows 11 and Windows Server 2025 systems in the next maintenance cycle, and sooner on shared workstations and Remote Desktop or terminal servers.
- Verify the affected and fixed versions on the MSRC page before rollout.
- Enforce least privilege and standard user accounts, and restrict interactive logon on shared or kiosk machines.
- Monitor for suspicious privilege changes and unexpected SYSTEM processes.
Information from Microsoft (Patch Tuesday November 2026)
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- MSRC advisory CVE-2026-83563 msrc.microsoft.com
- CVE Record CVE-2026-83563 www.cve.org
- Talos: Microsoft Patch Tuesday November 2026 blog.talosintelligence.com
- Qualys: Microsoft Patch Tuesday November 2026 review blog.qualys.com
- Strix CVE-2026-83563 (third party, unverified versions) www.strix.ai
- Trinety November 2026 Patch Tuesday (third party, KB unverified) trinetriops.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 11 Nov 2026, 03:23.
Original description (NVD)
Heap-based buffer overflow in Winlogon 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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