From the ISS
advisory:
"Vixie Cron is a scheduling daemon that ships with several Linux
distributions. Vixie Cron version 3.0pl1 could allow a local attacker to
gain root privileges. Crontab fails to properly drop privileges in certain
cases after a crontab modification operation. A local attacker could
exploit this vulnerability to gain root privileges on the system since
crontab is installed setuid root."
Note: this vulnerability is dated May 07 2001, and was first mentioned in
LWN on the May 10,
2001 security page.