Xen 3.1.1 allows virtual guest system users to cause a denial of service (hypervisor crash) by using a debug register (DR7) to set certain breakpoints.
lists.opensuse.org/opensuse-security-announce/2008-01/msg00002.html
lists.xensource.com/archives/html/xen-devel/2007-10/msg01048.html
secunia.com/advisories/28405
secunia.com/advisories/28412
secunia.com/advisories/28636
www.novell.com/linux/security/advisories/suse_security_summary_report.html
www.securityfocus.com/bid/27219