Xen 3.3.x through 4.5.x does not properly restrict write access to the host MSI message data field, which allows local x86 HVM guest administrators to cause a denial of service (host interrupt handling confusion) via vectors related to qemu and accessing spanning multiple fields.
https://support.citrix.com/article/CTX206006
https://security.gentoo.org/glsa/201604-03
http://xenbits.xen.org/xsa/advisory-128.html
http://www.ubuntu.com/usn/USN-2630-1
http://www.securitytracker.com/id/1032456
http://www.securityfocus.com/bid/74947
http://www.debian.org/security/2015/dsa-3286
http://www.debian.org/security/2015/dsa-3284
http://support.citrix.com/article/CTX201145
http://lists.opensuse.org/opensuse-security-announce/2015-06/msg00030.html
http://lists.opensuse.org/opensuse-security-announce/2015-06/msg00029.html
http://lists.opensuse.org/opensuse-security-announce/2015-06/msg00007.html
http://lists.opensuse.org/opensuse-security-announce/2015-06/msg00004.html
http://lists.fedoraproject.org/pipermail/package-announce/2015-June/160685.html
http://lists.fedoraproject.org/pipermail/package-announce/2015-June/160171.html
http://lists.fedoraproject.org/pipermail/package-announce/2015-June/160154.html