It’s a poorly written C minor with a major 7th (B natural) over Eb. Usually, + means an augmented 5th, but in a minor chord an augmented 5th doesn’t exist. Raising the G to Ab in a C minor chord changes it to an Ab chord. That said, this is a good example of how certain chord symbol shorthands can be more confusing in certain situations. Cm(maj7)/Eb (or similar approaches, can’t do superscript in the comments here)would be much clearer here.