oxenstored in Xen 4.1.x, Xen 4.2.x, and xen-unstable does not properly consider the state of the Xenstore ring during read operations, which allows guest OS users to cause a denial of service (daemon crash and host-control outage, or memory consumption) or obtain sensitive control-plane data by leveraging guest administrative access.
http://xenbits.xen.org/gitweb/?p=xen.git%3Ba=commit%3Bh=61401264eb00fae4ee4efc8e9a5067449283207b
http://xenbits.xen.org/gitweb/?p=xen.git%3Ba=commit%3Bh=40f9c5e0a6d15b4ca1f6d4ed3a46f0871520eab5
http://security.gentoo.org/glsa/glsa-201309-24.xml