Xen 4.2.x through 4.5.x does not initialize certain fields, which allows certain remote service domains to obtain sensitive information from memory via a (1) XEN_DOMCTL_gettscinfo or (2) XEN_SYSCTL_getdomaininfolist request.
https://security.gentoo.org/glsa/201604-03
http://xenbits.xen.org/xsa/advisory-132.html
http://www.securitytracker.com/id/1032158
http://www.securityfocus.com/bid/74248
http://www.debian.org/security/2015/dsa-3414
http://lists.opensuse.org/opensuse-security-announce/2015-06/msg00001.html
http://lists.opensuse.org/opensuse-security-announce/2015-05/msg00019.html
http://lists.opensuse.org/opensuse-security-announce/2015-05/msg00018.html
http://lists.fedoraproject.org/pipermail/package-announce/2015-May/157006.html
http://lists.fedoraproject.org/pipermail/package-announce/2015-May/156979.html
http://lists.fedoraproject.org/pipermail/package-announce/2015-April/156005.html