Privilege escalation in polkit pkexec

1) Input validation error

EUVDB-ID: #VU60007

Risk: Medium

CVSSv4.0: 8.5 [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:A/U:Green]

CVE-ID: CVE-2021-4034

CWE-ID: CWE-20 - Improper input validation

Exploit availability: Yes

Description

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

The vulnerability exists due to improper handling of the calling parameters count in the pkexec setuid binary, which causes the binary to execute environment variables as commands. A local user can craft environment variables in a way that they will be processed and executed by pkexec and execute arbitrary commands on the system as root.

Mitigation

Install update from vendor's website.

Vulnerable software versions

polkit: 0.92 - 0.120

CPE2.3

• cpe:2.3:a:freedesktop_org:polkit:0.92:*:*:*:*:*:*:*
• cpe:2.3:a:freedesktop_org:polkit:0.93:*:*:*:*:*:*:*
• cpe:2.3:a:freedesktop_org:polkit:0.94:*:*:*:*:*:*:*

External links

http://gitlab.freedesktop.org/polkit/polkit/-/commit/a2bf5c9c83b6ae46cbd5c779d3055bff81ded683
http://bugzilla.redhat.com/show_bug.cgi?id=2025869

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.