The minnows looked on course to claim a famous victory in their fifth-round tie, only to concede in the closing stages.
The Basque side were moments away from taking an advantage into next month's return leg after Txema Anibarro netted on 74 minutes.
But Malaga, fourth in the Primera Division, hit back to earn a 1-1 draw thanks to their on-loan United States international Onyewu.
And the top-flight side are now firm favourites to progress in the second leg.







