Networkmanager-sstp: networkmanager-sstp: local privilege escalation to root via shell injection in vpn profile fields

A flaw was found in NetworkManager-sstp, the SSTP VPN plugin for NetworkManager. A local unprivileged user can exploit this vulnerability by embedding special characters, known as shell metacharacters, into VPN connection profile fields such as CA certificate or proxy settings. These unescaped characters are then processed by the `pppd` daemon, which runs with root privileges, allowing the attacker to execute arbitrary commands with elevated permissions when a malicious VPN connection is activated.