CVE-2021-31961: Windows InstallService Elevation of Privilege Vulnerability

Overview

Severity

Medium (CVSS 6.1)

CVSS Vector

CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H/E:U/RL:O/RC:C

Category

Elevation of Privilege

Exploit Status

Not Exploited

Exploitation Likelihood

Less Likely

Patch Tuesday

2021-Jul

Released

2021-07-13

EPSS Score

0.32% (percentile: 55.4%)

FAQ

What privileges could be gained by an attacker who successfully exploited the vulnerability? An attacker would only be able to delete targeted files on a system. They would not gain privileges to view or modify file contents.

Affected Products (19)

Windows

• Windows 10 Version 1809 for 32-bit Systems
• Windows 10 Version 1809 for x64-based Systems
• Windows 10 Version 1809 for ARM64-based Systems
• Windows Server 2019
• Windows Server 2019 (Server Core installation)
• Windows 10 Version 1909 for 32-bit Systems
• Windows 10 Version 1909 for x64-based Systems
• Windows 10 Version 1909 for ARM64-based Systems
• Windows 10 Version 21H1 for x64-based Systems
• Windows 10 Version 21H1 for ARM64-based Systems
• Windows 10 Version 21H1 for 32-bit Systems
• Windows 10 Version 2004 for 32-bit Systems
• Windows 10 Version 2004 for ARM64-based Systems
• Windows 10 Version 2004 for x64-based Systems
• Windows Server, version 2004 (Server Core installation)
• Windows 10 Version 20H2 for x64-based Systems
• Windows 10 Version 20H2 for 32-bit Systems
• Windows 10 Version 20H2 for ARM64-based Systems
• Windows Server, version 20H2 (Server Core Installation)

Security Updates (3)

• 5004244
• 5004245
• 5004237

Acknowledgments

JeongOh Kyea (@kkokkokye) of THEORI working with <a href="https://www.zerodayinitiative.com/">Trend Micro Zero Day Initiative</a>

Revision History

• 2021-07-13: Information published.