Although Somma has made just one Leeds appearance he has been scoring goals regularly during his loan spell with League Two side Lincoln.
The 25-year-old has hit eight goals in 12 league starts, form that has prompted Leeds to secure his future.
Simon Grayson is pleased with Somma's progress at Sincil Bank and is looking forward to working with him next season.
"Dave has done really well at Lincoln," he told the club's official website. "The main reason behind him going out on loan was to play games in a competitive environment. We've seen his qualities in training and in the reserves, but he needed a loan move like this and his record down there speaks for itself.
"Dave will come back here with plenty of confidence, more experience, he knows his future here is secure with another year, and we look forward to working with him again."