A certain Red Hat patch for the Linux kernel in Red Hat Enterprise Linux (RHEL) 4 on the ia64 platform allows local users to use ptrace on an arbitrary process, and consequently gain privileges, via vectors related to a missing ptrace_check_attach call.
https://bugzilla.redhat.com/show_bug.cgi?id=572007
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A8687
http://support.avaya.com/css/P8/documents/100090459