Privilege escalation in Microsoft Windows Setup

1) Link following

EUVDB-ID: #VU58955

Risk: Low

CVSSv4.0: 5.9 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear]

CVE-ID: CVE-2021-43237

CWE-ID: CWE-59 - Improper Link Resolution Before File Access ('Link Following')

Exploit availability: No

Description

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

The vulnerability exists due to insecure link following in Windows Setup. A local user can create a symbolic link to arbitrary file on the system and overwrite it.

Successful exploitation of the vulnerability allows privilege escalation but requires that an administrator must begin a version update of Windows.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

Windows: 10 - 11 21H2 10.0.22000.194

Windows Server: 2019 10.0.17763.1 - 2019 2004

CPE2.3

• cpe:2.3:o:microsoft:windows:*:*:*:*:*:*:*:*
• cpe:2.3:o:microsoft:windows:10:Gold:*:*:*:*:*:*
• cpe:2.3:o:microsoft:windows:10:S:*:*:*:*:*:*
• cpe:2.3:o:microsoft:windows:10:Mobile:*:*:*:*:*:*
• cpe:2.3:o:microsoft:windows:10_20H2:10.0.19042.572:*:*:*:*:*:*
• cpe:2.3:o:microsoft:windows:10_21H1:10.0.19043.985:*:*:*:*:*:*
• cpe:2.3:o:microsoft:windows:10_21H2:10.0.19044.1288:*:*:*:*:*:*
• cpe:2.3:o:microsoft:windows:10_1607:10.0.14393.10:*:*:*:*:*:*
• cpe:2.3:o:microsoft:windows_server:2019:10.0.17763.1:*:*:*:*:*:*

External links

https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-43237
https://www.zerodayinitiative.com/advisories/ZDI-22-018/

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?

No. We are not aware of malware exploiting this vulnerability.