Cobblers manager Aidy Boothroyd is pleased with the arrival of the 20-year-old, who can play at right-back and in midfield.
"I saw Danny play for Hull City in pre-season and I was very impressed," he said.
"He is athletic, tough, he gets stuck in and he has a real hunger to do well and that is exactly the sort of character we are delighted to bring to the club.
"We have a busy period ahead, Danny will be a good addition for us and I would like to thank Steve Bruce for allowing us to borrow Danny."
East is available to play for Town in the League Cup and the Johnstone's Paint Trophy, and will remain with the League Two outfit until after the game at Burton Albion on September 29.