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.
www.securityfocus.com/bid/107378
lists.debian.org/debian-lts-announce/2019/03/msg00025.html
lists.debian.org/debian-lts-announce/2021/10/msg00029.html
lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/6DU7HAUAQR4E4AEBPYLUV6FZ4PHKH6A2/
salsa.debian.org/debian/cron/commit/26814a26