CVE-2026-81963: Windows Update Stack Elevation of Privilege Vulnerability

Overview

Severity
High (CVSS 7.8)
CVSS Vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C
Category
Elevation of Privilege
Exploit Status
Actively Exploited
Exploitation Likelihood
Detected
Patch Tuesday
2026-Sep
Released
2026-09-08
Last Updated
2026-10-07
EPSS Score
0.39% (percentile: 32.4%)
CISA KEV
Listed — due 2026-09-22

Description

Improper link resolution before file access ('link following') in Windows Update Stack allows an authorized attacker to elevate privileges locally.

FAQ

What privileges could be gained by an attacker who successfully exploited this vulnerability? An attacker who successfully exploited this vulnerability could gain SYSTEM privileges.

Detection & Weaponization (1 sources)

Maturity: Exploit

  • GitHub PoC: 1 repositories

Affected Products (10)

Windows

  • Windows Server 2025 (Server Core installation)
  • Windows 11 Version 25H2 for ARM64-based Systems
  • Windows 11 Version 25H2 for x64-based Systems
  • Windows 11 Version 23H2 for ARM64-based Systems
  • Windows 11 Version 23H2 for x64-based Systems
  • Windows 11 Version 24H2 for ARM64-based Systems
  • Windows 11 Version 24H2 for x64-based Systems
  • Windows Server 2025
  • Windows 11 version 26H1 for x64-based Systems
  • Windows 11 Version 26H1 for ARM64-based Systems

Security Updates (4)

Acknowledgments

Zhang WangJunJie with Hillstone Networks, <a href="https://fr.linkedin.com/in/romain-deperne&#128737;️-580920221">Romain DEPERNE</a>, Microsoft Threat Intelligence Centre (MSTIC), haowei yan, Zhang WangJunJie with Hillstone Networks, Microsoft Threat Intelligence Centre (MSTIC)

Revision History

  • 2026-09-08: Information published.
  • 2026-09-11: Updated an acknowledgement. This is an informational change only.
  • 2026-09-15: Updated an acknowledgement. This is an informational change only.
  • 2026-10-06: Updated an acknowledgement. This is an informational change only.
  • 2026-10-07: Updated an acknowledgement. This is an informational change only.