The libvirt driver in OpenStack Compute (Nova) before 2015.1.4 (kilo) and 12.0.x before 12.0.3 (liberty), when using raw storage and use_cow_images is set to false, allows remote authenticated users to read arbitrary files via a crafted qcow2 header in an ephemeral or root disk.
https://security.openstack.org/ossa/OSSA-2016-007.html
https://bugs.launchpad.net/nova/+bug/1548450