The VGA emulator in QEMU allows local guest users to read host memory by setting the display to a high resolution.
https://bugzilla.redhat.com/show_bug.cgi?id=1139115
http://www.ubuntu.com/usn/USN-2409-1
http://www.securityfocus.com/bid/69654
http://www.debian.org/security/2014/dsa-3044
http://support.citrix.com/article/CTX200892
http://secunia.com/advisories/61829
http://rhn.redhat.com/errata/RHSA-2014-1941.html
http://rhn.redhat.com/errata/RHSA-2014-1670.html
http://rhn.redhat.com/errata/RHSA-2014-1669.html
http://lists.opensuse.org/opensuse-security-announce/2015-04/msg00014.html