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.
https://salsa.debian.org/debian/cron/commit/f2525567
https://lists.debian.org/debian-lts-announce/2021/10/msg00029.html
https://lists.debian.org/debian-lts-announce/2019/03/msg00025.html