kernel is vulnerable to privilege escalation. The vulnerability exists as a flaw was found in the way the Xen hypervisor implementation checked for the upper boundary when getting a new event channel port. A privileged guest user could use this flaw to cause a denial of service or escalate their privileges.
docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/5/html/5.6_Technical_Notes/kernel.html#RHSA-2011-0833
downloads.avaya.com/css/P8/documents/100145416
rhn.redhat.com/errata/RHSA-2011-0833.html
access.redhat.com/errata/RHSA-2011:0833
access.redhat.com/security/updates/classification/#important
bugzilla.redhat.com/show_bug.cgi?id=701240