Signed by Tony Mowbray on a season-long deal, Varga has maintained his place in the side under Aitor Karanka.
Varga has spent most of the season at right-back - although he has also featured in central midfield.
He has started 28 games in total, and has been one of Boro's most consistent performers throughout the campaign.
But with two years left on his deal at Debrecen, Boro have yet to confirm whether they will be looking to sign him on a permanent basis.
Debrecen have now announced that Middlesbrough have until May 20 to decide whether to keep Varga or not - after which date their option on him expires.