Here's a list of people that the House Un-American Activities Committee believed to be members of the CPUSA. One was an avowed Communist, one or two more there's a strong possibility of them being members and the rest probably weren't.
It's well worth remembering that Samuel Dickstein one of the founders of HUAC was a verified and confirmed NKVD agent. He wasn't a communist though. He merely turned traitor for cash and a relatively low amount as well.
https://en.wikipedia.org/wiki/Samuel_Dickstein_(congressman)#McCormack-Dickstein_Committee