api/metadata/handler.py in OpenStack Compute (Nova) before 2013.2.4, 2014.x before 2014.1.2, and Juno before Juno-2, when proxying metadata requests through Neutron, makes it easier for remote attackers to guess instance ID signatures via a brute-force attack that relies on timing differences in responses to instance metadata requests.
Exposure of Sensitive Information to an Unauthorized Actor The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information.