The initial fail2ban virtual memory overhead on the server was approximately 350MB.
While that is a lot, you’re not stuck with it. You can modify the over-sized default stack size by adding one line of code to the configuration file.
To limit the memory used by fail2ban, edit /etc/default/fail2ban and add this line to the end of the file.
ulimit -s 256
This sets the default stack size to 256 KB and lowers the memory consumption of fail2ban. Lastly, restart fail2ban.
Also this bug should have been addressed in newer versions, so make sure to update it to the latest.