Scott Arfield scored early on and Kemar Roofe added a spectacular second goal after 69 minutes but the Portuguese side netted twice in three minutes towards the end as it finished all square.
Rangers and Benfica remain on course to qualify for the knock-out stage and could seal their places next week, with Steven Gerrard's men at home to Standard Liege on matchday five before travelling to Poland to play Lech Poznan the following week.
However, Celtic's hopes of progressing from Group H are over after they lost 4-1 against Sparta Prague in the Czech Republic.