Citrix XenServer 5.0 Update 2 and earlier, and 5.5 Update 1 and earlier, when using a pvops kernel, allows guest users to cause a denial of service in the host via unspecified vectors that trigger "incorrectly set flags."

Citrix XenServer 4.1, 6.0, 5.6 SP2, 5.6 Feature Pack 1, 5.6 Common Criteria, 5.6, 5.5, 5.0, and 5.0 Update 3 contains a Local Privilege Escalation Vulnerability which could allow local users with access to a guest operating system to gain elevated privileges.