init_dev in tty_io.c in the Red Hat backport of NPTL to Red Hat Enterprise Linux 3 does not properly clear controlling tty's in multi-threaded applications, which allows local users to cause a denial of service (crash) and possibly gain tty access via unknown attack vectors that trigger an access of a pointer to a freed structure.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A9435