Threat Intelligence / CVE / CVE-2021-4034

CVE-2021-4034 — Polkit

CISA KEV
CVSS v3.1 7.8 (HIGH) · EPSS 87.8% (higher than 99.4% of all scored CVEs) · Priority 9/10 · Published 2022-01-28

As of 2025-11-06, CVE-2021-4034 is a HIGH-severity vulnerability in Polkit, CVSS v3.1 7.8, EPSS 87.8% (99.4th percentile). It is listed in the CISA Known Exploited Vulnerabilities catalog (added 2022-06-27), with a US federal remediation deadline of 2022-07-18. Threadlinqs Intelligence links 3 tracked threat campaigns to CVE-2021-4034, most recently “PCPJack Covert SMTP Relay Network — 230 Hijacked AWS/Google Cloud/Azure Servers via Sliver C2 + Chisel SOCKS Tunneling”.

Last updated: 2025-11-06

What is CVE-2021-4034?

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.

The record classifies CVE-2021-4034 under weakness classes CWE-787, CWE-125. Its CVSS v3 base vector states that the flaw requires local access to the host, needs low-privilege credentials, needs no user interaction, and has high impact on confidentiality, integrity, availability. 55 affected-product entries are recorded, across 2 vendors, listed below. The identifier was first published 1689 days ago.

Severity and exploitation probability

CVSS v3.1 base score
7.8 — HIGH
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS (FIRST)
87.8% probability of exploitation in the next 30 days, higher than 99.4% of all scored CVEs
CISA KEV
Listed since 2022-06-27, federal remediation deadline 2022-07-18
Threadlinqs priority
9/10 — CISA KEV-listed, which Threadlinqs floors at 9
Published
2022-01-28, last modified 2025-11-06

Is CVE-2021-4034 being exploited?

CISA added CVE-2021-4034 to the Known Exploited Vulnerabilities catalog on 2022-06-27, which means the agency holds evidence of exploitation in the wild; US federal civilian agencies had to remediate it by 2022-07-18 under BOD 22-01. It currently carries a trending score of 40 in the Threadlinqs vulnerability feed.

Affected products and versions

Showing 25 of 55 recorded product entries.

How to fix CVE-2021-4034

The record marks a vendor fix as available for CVE-2021-4034. Patch reference: https://github.com/polkit-org/polkit/commit/a2bf5c9c83b6ae46cbd5c779d3055bff81ded683. Vendor advisory: https://access.redhat.com/security/vulnerabilities/RHSB-2022-001. Because CVE-2021-4034 is KEV-listed, US federal civilian agencies were required to apply the vendor fix, or stop using the product, by 2022-07-18. Apply the vendor fix referenced above to every affected product listed in this record, then confirm the running version against the vendor advisory.

Threat activity tracking CVE-2021-4034

3 tracked threats in the Threadlinqs corpus reference CVE-2021-4034, either in the campaign’s CVE list or as an indicator on the campaign record.

Sources

Seeded from nvd and not yet processed by the Threadlinqs enrichment pipeline, so blank CVSS, EPSS or KEV fields above mean NOT MEASURED rather than measured-absent.

Full detection coverage & IOCs for threats exploiting CVE-2021-4034 are available via the Threadlinqs MCP server (Purple tier). View plans →

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