He has until June 2023 to extend his current contract, although he has not yet agreed to a new deal with the club.
During a recent interview with Sky Sports, Mohamed Salah discussed the present issue, which you can see in the tweet below.

Salah is currently the leading scorer in the Premier League, so it's no surprise that Liverpool want to extend his contract.

Salah claimed in the interview that he has stated his desires, but that Liverpool has yet to respond with an offer.