In the cron package through 3.0pl1-128 on Debian, and through 3.0pl1-128ubuntu2 on Ubuntu, the postinst maintainer script allows for group-crontab-to-root privilege escalation via symlink attacks against unsafe usage of the chown and chmod programs.

vixie-cron: memory consumption DoS via a large crontab file

Vixie Cron before the 3.0pl1-133 Debian package allows local users to cause a denial of service (memory consumption) via a large crontab file because an unlimited number of lines is accepted.

vixie-cron: calloc return value resulting in remote dos

Vixie Cron before the 3.0pl1-133 Debian package allows local users to cause a denial of service (daemon crash) via a large crontab file because the calloc return value is not checked.