Libcontainer 1.6.0, as used in Docker Engine, allows local users to escape containerization ("mount namespace breakout") and write to arbitrary file on the host system via a symlink attack in an image when respawning a container.

Libcontainer and Docker Engine before 1.6.1 opens the file-descriptor passed to the pid-1 process before performing the chroot, which allows local users to gain privileges via a symlink attack in an image.