Any local root vulnerability will also work in a container, eg this one http://www.ubuntu.com/usn/usn-1914-1/ http://www.ubuntu.com/usn/usn-1914-1/ - note that

Any local root vulnerability will also work in a container, eg this one http://www.ubuntu.com/usn/usn-1914-1/ http://www.ubuntu.com/usn/usn-1914-1/ - note that a lot of kernel vulnerabilities are never really announced, just quietly fixed.