CVE-2012-0055 on Ubuntu 12.04 LTS (precise) - medium.
Description:
Using overlayfs with lxc causes tty problems that can kill X. Overlayfs needs to honor the necessary cgroup permission calls. Andy Whitcroft discovered a that the Overlayfs filesystem was not doing the extended permission checks needed by cgroups and Linux Security Modules (LSMs). A local user could exploit this to by-pass security policy and access files that should not be accessible.