The instance rescue mode in OpenStack Compute (Nova) 2013.2 before 2013.2.3 and Icehouse before 2014.1, when using libvirt to spawn images and usecowimages is set to false, allows remote authenticated users to read certain compute host files by overwriting an instance disk with a crafted image.
The Nova scheduler in OpenStack Compute (Nova) Folsom (2012.2) and Essex (2012.1), when DifferentHostFilter or SameHostFilter is enabled, allows remote authenticated users to cause a denial of service (excessive database lookup calls and server hang) via a request with many repeated IDs in the os:schedulerhints section.