Polkit pkexec Local Privilege Escalation Vulnerability
Actively exploited in the wild. Patch or mitigate immediately — don't wait for a maintenance window.
An attacker with a basic user account, with local access to the host, with no user interaction, can fully compromise the system — steal data, tamper with it and take it offline.
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.
Techniques marked “observed” are corroborated by threat intelligence; the rest are inferred from the weakness type (CWE) and attack vector.
Corroborated threat activity referencing this CVE — with source and confidence, not inference.
These techniques were analysed against this CVE's real-world exploitation — the matching entries in the ATT&CK chain above are marked “observed”.
Generated by Wavense from the CVE record — an immediate mitigation and the permanent fix.
Until patches are applied, monitor `pkexec` usage for anomalous behavior or execution by non-standard processes or users. Restrict local user access and implement strong endpoint detection and response (EDR) solutions. As a temporary measure, consider removing the setuid bit from `/usr/bin/pkexec`, but test thoroughly as this may break legitimate functionality.
The permanent fix is to apply vendor-provided patches for polkit. Upgrade the `polkit` package to a version that specifically addresses CVE-2021-4034 (e.g., polkit 0.120 or later). Consult your operating system vendor's security advisories for specific package versions and installation instructions relevant to your distribution.
An attacker can exploit this vulnerability to execute arbitrary code with root privileges, achieving complete local privilege escalation. This allows unprivileged users to gain administrative control over the system, leading to full system compromise, data exfiltration, or service disruption.
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