Networked
A file-upload form validates image extension and MIME magic bytes but permits a PHP double extension, which an Apache handler misconfiguration executes, yielding a shell as www-data. A cron job running as guly passes uploaded filenames unsanitised to exec(), so a filename containing shell metacharacters achieves command injection and a shell as guly. guly may run a network-configuration script as root that reads interface values into a config file, and a known ifcfg script-injection flaw turns those values into root command execution.