The FireEye MPS (Malware Protection System) is vulnerable to a remote code execution vulnerability, simply from monitoring hostile traffic. FireEye is designed to operate as a passive network tap, so that it can see all the files and emails that enter a monitored network. This vulnerability allows an attacker to compromise the FireEye device, get a root shell and start monitoring all traffic on the victim network (emails, attachments, downloads, web browsing, etc). This is about the worst possible vulnerability that you can imagine for a FireEye user, it literally does not get worse than this.