Vulnerability identifier: #VU58367

Vulnerability risk: High

CVSSv3.1: 8.4 [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]

CVE-ID: CVE-2021-43890

CWE-ID: CWE-264

Exploitation vector: Local

Exploit availability: Yes

Vulnerable software:
Windows
Operating systems & Components / Operating system
Windows Server
Operating systems & Components / Operating system

Vendor: Microsoft

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.

Mitigation
Install update from vendor's website.

Vulnerable software versions

Windows: 10 - 10 S

Windows Server: 2019 - 2022

---

External links
http://github.com/klinix5/InstallerFileTakeOver
http://blog.talosintelligence.com/2021/11/attackers-exploiting-zero-day.html
http://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-43890

---

Q & A

Can this vulnerability be exploited remotely?

No. This vulnerability can be exploited locally. The attacker should have authentication credentials and successfully authenticate on the system.

Is there known malware, which exploits this vulnerability?

Yes. This vulnerability is being exploited in the wild.