With Osasuna just one place below Malaga in La Liga, a close encounter was expected at Estadio La Rosaleda for the first leg of the fourth-round clash.
Yet Malaga initially assumed complete control, taking a two-goal lead into the break thanks to strikes from defenders Sergio Sanchez and Antunes, before Juanmi made it 3-0 two minutes into the second half.
Javi Gracia's men launched a stunning comeback on the back of Roberto Torres' 57th-minute strike.
Manuel pulled another back and Emiliano Armenteros made light of Raoul Loe's sending off by equalising in the 78th minute.
Malaga's Ignacio Camacho was also dismissed in a fiery end to the eventful encounter.
There were four other first-leg ties played on Sunday, with Espanyol also coming from behind in a 2-2 draw at Real Jaen.
David Lopez gave Espanyol the lead on the stroke of half-time, but a Sidnei own goal and a Jozabed Sanchez strike looked to have given the second-tier side victory.
Uruguayan Christian Stuani had other ideas, equalising with two minutes left.
Odion Ighalo scored a double as Granada beat Alcorcon 2-0, while 10-man Almeria won 3-1 at Las Palmas and Valencia, who had Jonas sent off, drew 0-0 at Gimnastic Tarragona.
All second-leg clashes will be played in the week commencing December 16.
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