NetworkManager-l2tp through 1.52.4, fixed in 1.52.6, contains a privilege escalation vulnerability that allows local users with permission to create VPN connections to execute arbitrary code as root by injecting pppd options through a crafted VPN username. Attackers can embed a double-quote character or whitespace in the username to break out of the pppd options file quoting context and include the pppd plugin directive, causing the privileged pppd process to load an attacker-controlled shared object.