Four men, three of whom were armed with baseball bats or metal bars, entered the property in the Queens Avenue area at about 21:50 BST on Friday.
Police said the victim sustained injuries to both of his legs and was taken to hospital.
His injuries are not thought to be life-threatening.
A 19-year-old man has been taken to hospital after being beaten by a gang at a house in Glengormley, County Antrim.