Borini, who signed from Roma in July but has yet to score in the league, sustained a foot injury in the league clash with Manchester United last month.
He then aggravated the problem, resulting in a fracture, while training with the Italian under-21 side last week.
"Typically, an injury of this nature requires a three-month rehabilitation period," Liverpool said in a statement on their website.
His absence means Liverpool have just the one recognised striker - Uruguayan Luis Suarez - until the January transfer window.
The Anfield club, who let England striker Andy Carroll go out on loan to West Ham United, have endured one of their worst starts to a top flight season, winning just one of their opening seven league matches.
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