CVE-2021-4034: Red Hat Polkit exploited

Advisory generated from the CVE record, CISA, Exploit Observer and VEDAS: what it is, whether it is exploited, who is affected, and how to fix and detect it.

What it is

A local privilege escalation vulnerability was found on polkit’s pkexec utility. The pkexec application is a setuid tool designed to allow unprivileged users to run commands as privileged users according predefined policies. The current version of pkexec doesn’t handle the calling parameters count correctly and ends trying to execute environment variables as commands. An attacker can leverage this by crafting environment variables in such a way it’ll induce pkexec to execute arbitrary code. When successfully executed the attack can cause a local privilege escalation given unprivileged users administrative rights on the target machine.

Description quoted from the CVE record (assigned by redhat, published 2022-01-28).

Weakness: (CWE-787|CWE-125)

How it can be exploited

Exploitable with local access with low attack complexity needing low privileges and no user interaction. Impact: confidentiality high, integrity high, availability high. CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CISA assessment (SSVC): CISA assesses exploitation as active. Automatable: no. Technical impact: total.

On CISA KEV since: 2022-06-27
US federal deadline: 2022-07-18
Ransomware use: Yes

Public exploit evidence (Exploit Observer)

Exploit Observer found 1 Metasploit module, 1 Exploit-DB entry, 219 code repositories and 11 research write-ups naming this CVE.

Code repositories that name a CVE are often scanners, copies or fakes, and some are malware. Read the code before running anything.

See all 256 references on Exploit Observer

Live scores

EPSS: 0.949
very likely to be attacked soon
VEDAS: 0.980
strong exploit evidence
On CISA KEV: Yes, since 2022-06-27
Detection rule: Out of scope (local)

EPSS (chance of attack)

VEDAS (exploit evidence)

Thin horizontal line: the “likely exploited” threshold (EPSS 0.10, VEDAS 0.5). Shaded “no data” areas are periods when cve-scores did not publish.

Who is affected

Product	Affected	Not affected
polkit	version all	Not stated

Version ranges exactly as the CVE record states them. “Before X” means X is the first fixed version.

How to fix it

CISA required action: Apply updates per vendor instructions.

Vendor guidance:

https://nvd.nist.gov/vuln/detail/CVE-2021-4034

How to detect it

This bug needs local access to exploit. VEDAS signatures cover remotely exploitable bugs for now, so there is no network rule or remote check for it. Patch it and watch your endpoint telemetry for unusual local activity.

Advisories on this CVE

Operation Snowball: Jailbroken AI agent hits European telecom (full advisory)

References

Government sources

https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-4034 (government-resource)

Other references

Other databases

Where this comes from

This advisory is generated automatically by VEDAS from: CVE.org record, CISA KEV, cve-scores (EPSS and VEDAS), Exploit Observer. Text in quotes is reproduced from the source; everything else is a fixed template filled with source fields. Nothing here is written by a language model. Check the vendor advisory before acting, and read how VEDAS and Exploit Observer work, and their limits.