Zero-day vulnerability in Windows

Permissions, Privileges, and Access Controls
CVE-2021-43890

Known malware:

Emotet, Trickbot, Bazaloader

Vulnerability details

Advisory: SB2021112505 - Privilege escalation in Microsoft Windows

Vulnerable component: Windows

CVE-ID: CVE-2021-43890

CVSSv3 score: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H/E:H/RL:O/RC:C

CWE-ID: CWE-264 - Permissions, Privileges, and Access Controls

Description:

The vulnerability allows a local user to escalate privileges on the system.

The vulnerability exists due to incorrect permissions in windows installer service. A local user can run a specially crafted program to execute arbitrary code with SYSTEM privileges.

The vulnerability exists due to incomplete patch for #VU58061 (CVE-2021-41379).

Note, the vulnerability is being actively exploited in the wild.

External links:

https://blog.talosintelligence.com/2021/11/attackers-exploiting-zero-day.html

https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2021-43890


About zero-day vulnerabilities

Zero-day vulnerability is an undisclosed vulnerability in software that hackers can exploit to compromise computer programs, gain unauthorized access to sensitive data, penetrate networks, etc. We consider vulnerability a zero-day when there is no solution provided from software vendor and the vulnerability is being actively exploited by malicious actors.

Zero-day candidate is a potential zero-day vulnerability in software which might have been used in targeted attacks, however there is no evidence to support this suggestion.