CVE-2021-4034: high-severity vulnerability in polkit

A flaw in polkit's pkexec tool allows unprivileged users to run arbitrary commands with administrator privileges by manipulating environment variables. This happens because pkexec incorrectly processes its input parameters and accidentally executes environment variables as if they were commands.

CVE-2021-4034 is a buffer overflow (CWE-787) in pkexec's argument parsing that causes it to interpret environment variables as executable commands. An unprivileged local attacker can craft malicious environment variables to achieve arbitrary code execution with root privileges; the vulnerability requires only local access and no authentication, resulting in complete privilege escalation.