The 27-year-old made the switch to Molineux last summer on a three-year contract from Rapid Vienna for an initial £1.8 million fee.
Maierhofer had scored 27 goals during the 2008-2009 campaign for his club and forced his way into the Austrian national team, but he failed to make a similar sort of impact at Wolves and has been told he can leave.
Maierhofer managed just one goal for the midlands club before he suffered a hernia problem and had slipped out of first team contention by the time he returned to fitness in the New Year.
He spent a month on loan at Bristol City, following in the footsteps of Chris Iwelumo who also had a temporary spell at Ashton Gate.
McCarthy said: "Stefan is for sale. He is, yes. I tell the players if they can go and then I guess they tell their agents who go and drum up a bit of business - and get the business done.
"There is a bit of interest in Stefan from abroad."
Maierhofer found himself behind the likes of Kevin Doyle, Sylvan Ebanks-Blake and Iwelumo and the arrival this summer of Steven Fletcher from Burnley meant a parting of ways was almost inevitable.