Citrix has acknowledged multiple vulnerabilities in XenServer, which can be exploited by malicious, local users in a guest virtual machine to cause a DoS (Denial of Service) and potentially gain escalated privileges.

For more information:
SA51397

The vulnerabilities are reported in versions 6.1 and prior.

Solution
Apply hotfixes (please see the vendor's advisory for details).
Original Advisory
http://support.citrix.com/article/CTX135777

Other references
Further details available to Secunia VIM customers

Deep Links
Links available to Secunia VIM customers