Xen 4.3.x and earlier does not properly handle certain errors, which allows local HVM guests to obtain hypervisor stack memory via a (1) port or (2) memory mapped I/O write or (3) other unspecified operations related to addresses without associated memory.
lists.opensuse.org/opensuse-security-announce/2014-03/msg00015.html
lists.opensuse.org/opensuse-security-announce/2014-03/msg00021.html
lists.opensuse.org/opensuse-security-announce/2014-04/msg00000.html
lists.opensuse.org/opensuse-updates/2013-11/msg00009.html
rhn.redhat.com/errata/RHSA-2013-1790.html
security.gentoo.org/glsa/glsa-201407-03.xml
www.debian.org/security/2014/dsa-3006
www.openwall.com/lists/oss-security/2013/09/30/1