The exec node is only really designed to run "one" command. you may be able to do something like
echo | mount.cifs //192.168.1.58/Share /Recepten –o user=Iedereen
that may work - or the enter may get sent too quick...
The node-red-node-daemon node could be an alternative as that leaves the input side open for use as stdin so you can inject extra commands into the process at any time.