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

For more information:
SA49789
SA50191
SA50472

1) An error in the VNC terminal emulator when handling certain escape sequences can be exploited by a guest VM to gain control of the Dom0 domain.

The vulnerabilities are reported in versions 6.0.2 and prior.

Solution
Apply hotfixes.
Further details available to Secunia VIM customers

Provided and/or discovered by
1) James Forshaw, Context Information Security.

Changelog
Further details available to Secunia VIM customers

Original Advisory
Citrix:
http://support.citrix.com/article/CTX134708

Context Information Security:
http://archives.neohapsis.com/archives/fulldisclosure/2012-10/0249.html

Other references
Further details available to Secunia VIM customers

Deep Links
Links available to Secunia VIM customers