Tiny Core Linux 5.X and mounting Samba drives

I was fighting for a while to mount a network drive on my Tiny Core Linux box running v5.4 with the following error

mount error(13): Permission denied
Refer to the mount.cifs(8) manual page (e.g. man mount.cifs)

The command I was trying was:

sudo mount -t cifs // /mnt/popcorn -o username=$USER,password=$PASSWORD

After a lot of googling, it turns out that as per http://office-supply-liberation.blogspot.ie/2014/01/asus-ac66r-wireless-router-mounting.html, I need to add another option! Weird, since Tiny Core Linux 4.X mounts the exact same drive without requiring the option.

So the command that works is:

sudo mount -t cifs // /mnt/popcorn -o username=$USER,password=$PASSWORD,sec=ntlmv2