find value in string and drop everything else

I am trying to inventory the local computer store of my AD Domain remotely.

I am getting a comma delimited string back for the subject,and I would like to strip everything out of the string except for the value after CN=

CN won’t always be the 2nd field, it could be the first or third or fourth field.

E=bob.boberson@cityofchicago.org, CN=server1.management.chitown.local, OU=Infrastructure, O=City of Chicago, L=Chicago, S=IL, C=US 

I have no idea how to begin.

thanks,

Rogue