Samu fired the visitors ahead in the first half but Osasuna were handed some hope when Jesus Gamez was dismissed for a second booking just after the break.
However, Javi Gracia's men failed to take the initiative and Nordin Amrabat doubled the lead to move Malaga above their opponents on goal difference, three points above the drop zone.
Andres Fernandez was the first of the goalkeepers called into action as he palmed away Duda's long-range effort but moments later Oriol Riera should have given the home side the lead as he fired over the bar from six yards.
Willy Caballero was then on hand to keep Malaga on level terms as he made an impressive double save from first Damia and then Alvaro Cejudo, following Roberto Torres' corner.
But it was the visitors who took the lead in the 13th minute as Samu was on hand to volley home following Amrabat's cross.
Duda brought another save from Fernandez at the midway point of the first half but the best chances were coming down the other end with Caballero denying Torres before Jordan Loties hit the post with the rebound.
Both sides were having chances with Roque Santa Cruz for Malaga and Cejudo and Loties for Osasuna all wasting opportunities to score from set-pieces.
Gamez went in the book for dissent just before the break and the teams had only been back out eight minutes when he was given his marching orders for a second yellow card, following a foul on Torres.
The visitors continued to press forward, though, and Sergi Darder missed from distance before putting a header wide from a corner.
If anything, playing against 10-men seemed to have stunted Osasuna and it was Malaga who doubled their lead in the 66th minute as Amrabat slotted home after latching on to a Santa Cruz pass.
That did seem to spur the hosts to life as Torres brought a smart save from Caballero - but they could not find a way through in the closing stages.