Vixie Cron is vulnerable to denial of service. The vulnerability exists due to memory consumption via a large crontab file due to an unlimited number of lines being accepted into the system.
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/[email protected]/message/6DU7HAUAQR4E4AEBPYLUV6FZ4PHKH6A2/
salsa.debian.org/debian/cron/commit/26814a26
security-tracker.debian.org/tracker/CVE-2019-9705