Xen 3.x, possibly before 3.1.2, when running on IA64 systems, does not check the RID value for mov_to_rr, which allows a VTi domain to read memory of other domains.
lists.xensource.com/archives/html/xen-announce/2007-11/msg00000.html
lists.xensource.com/archives/html/xen-ia64-devel/2007-10/msg00189.html
osvdb.org/41341
secunia.com/advisories/27915
secunia.com/advisories/29236
www.redhat.com/support/errata/RHSA-2008-0154.html
www.securityfocus.com/bid/26716
oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A9471