The auto-reap of child processes in Linux kernel 2.6 before 2.6.15 includes processes with ptrace attached, which leads to a dangling ptrace reference and allows local users to cause a denial of service (crash) and gain root privileges.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A9080
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=174078
http://www.vupen.com/english/advisories/2005/2649
http://www.trustix.org/errata/2005/0070
http://www.securityfocus.com/bid/15625
http://www.securityfocus.com/archive/1/439623/100/100/threaded
http://www.securityfocus.com/archive/1/427981/100/0/threaded
http://www.securityfocus.com/archive/1/419522/100/0/threaded
http://www.securityfocus.com/advisories/9806
http://www.redhat.com/support/errata/RHSA-2006-0101.html
http://www.mandriva.com/security/advisories?name=MDKSA-2006:018
http://www.debian.org/security/2006/dsa-1017
http://secunia.com/advisories/19374
http://secunia.com/advisories/18510
http://secunia.com/advisories/18203
http://secunia.com/advisories/17918
http://secunia.com/advisories/17917