LXCFS before 0.12 does not properly enforce directory escapes, which might allow local users to gain privileges by (1) querying or (2) updating a cgroup.
https://github.com/lxc/lxcfs/commit/a8b6c3e0537e90fba3c55910fd1b7229d54a60a7
https://euvd.enisa.europa.eu/vulnerability/EUVD-2015-1481
https://bugs.launchpad.net/ubuntu/+source/lxcfs/+bug/1508481