CVE-2021-4034 — Polkit Vulnerability Details

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 1735 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): 94.3% probability of exploitation in the next 30 days, higher than 99.8% of all scored CVEs
CISA KEV: Listed since 2022-06-27, federal remediation deadline 2022-07-18 — used in known ransomware campaigns
Threadlinqs priority: 10/10 — CISA lists it as used in ransomware, which Threadlinqs scores at the maximum
Published: 2022-01-28, last modified 2026-08-15

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. CISA flags the vulnerability as one used in known ransomware campaigns. Weaponised exploit code for CVE-2021-4034 is publicly available. 11 public proof-of-concept repositories are tracked for this identifier. It currently carries a trending score of 58 in the Threadlinqs vulnerability feed.

Affected products and versions

Polkit Project: Polkit
Redhat: Enterprise Linux Server Update Services For Sap Solutions 7.6, Enterprise Linux Server Update Services For Sap Solutions 7.7, Enterprise Linux 8.0, Enterprise Linux Desktop 7.0, Enterprise Linux Eus 8.2, Enterprise Linux For Ibm Z Systems 7.0, Enterprise Linux For Ibm Z Systems 8.0, Enterprise Linux For Ibm Z Systems Eus 8.2, Enterprise Linux For Ibm Z Systems Eus 8.4, Enterprise Linux For Power Big Endian 7.0, Enterprise Linux For Power Little Endian 7.0, Enterprise Linux For Power Little Endian 8.0, Enterprise Linux For Power Little Endian Eus 8.1, Enterprise Linux For Power Little Endian Eus 8.2, Enterprise Linux For Power Little Endian Eus 8.4, Enterprise Linux For Scientific Computing 7.0, Enterprise Linux Server 6.0, Enterprise Linux Server 7.0, Enterprise Linux Server Aus 7.3, Enterprise Linux Server Aus 7.4, Enterprise Linux Server Aus 7.6, Enterprise Linux Server Aus 7.7, Enterprise Linux Server Aus 8.2, Enterprise Linux Server Aus 8.4

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

8 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.

Operation Escaneo: MexicanMafia (PanchoVilla) Intrusion Campaign Against Mexican Government Agencies and Latin American Financial Institutions — HIGH · 2026-10-23
Rapid7 Q3 2026 Threat Landscape: High-Severity Flaws Exploited in 3 Days as The Gentlemen and Qilin Ransomware Dominate — HIGH · 2026-10-21
CL-UNK-1211: AI-Powered Espionage Campaign Targets Government Linux Infrastructure (SysGoRAT, CVE-2025-55182, CVE-2021-4034) — HIGH · 2026-10-15
CyberXero: AI-Augmented Initial Access Broker Targeting Ukrainian Critical Infrastructure and Global WordPress/E-commerce Platforms — HIGH · 2026-10-07
Attacker Maintains Root-Level MeshCentral Backdoor Inside Thai ISP 3BB, Targets RADIUS Subscriber-Credential Databases (CVE-2024-21762 Toolkit Staged) — HIGH · 2026-09-15
PCPJack Covert SMTP Relay Network — 230 Hijacked AWS/Google Cloud/Azure Servers via Sliver C2 + Chisel SOCKS Tunneling — HIGH · 2026-06-07
SHADOW-AETHER-040 & SHADOW-AETHER-064 — Agentic AI-Driven Intrusion Campaigns Targeting LATAM Government and Financial Sectors (Vibe Hacking) — CRITICAL · 2026-05-12
CL-UNK-1068: China-Nexus APT Targeting Critical Infrastructure via DLL Sideloading, Xnote Backdoor, ScanPortPlus Scanner, and FRP Tunneling — HIGH · 2026-03-06

Sources

Enriched from CVE.org, FIRST EPSS, CISA KEV, GitHub Security Advisories, public proof-of-concept repositories. Last verified by Threadlinqs on 2026-10-10.

Other references

Showing 5 of 11 recorded references.