Linux VServer 1.27 and earlier, 1.3.9 and earlier, and 1.9.1 and earlier shares /proc permissions across all virtual and host servers, which allows local users with the ability to set permissions in /proc to obtain system information or cause a denial of service on other virtual servers or the host server.
https://exchange.xforce.ibmcloud.com/vulnerabilities/16626
http://www.securityfocus.com/bid/10660
http://securitytracker.com/id?1010643
http://secunia.com/advisories/12021
http://linux-vserver.org/ChangeLog
http://archives.neohapsis.com/archives/bugtraq/2004-07/0040.html