Unspecified vulnerability in Citrix XenServer 5.0 Update 3 and earlier, and 5.5, allows local users to bypass authentication and execute unspecified Xen API (XAPI) calls via unknown vectors.
http://www.vupen.com/english/advisories/2010/0290
http://www.securitytracker.com/id?1023530
http://www.securityfocus.com/bid/38052
http://support.citrix.com/article/CTX123460
http://support.citrix.com/article/CTX123456