Unpredictable Napoli held by Bologna
Napoli, who lack the strength in depth to perform consistently at their best, fell behind after 14 minutes when Nico Pulzetti found Robert Acquafresca, giving him a clear run on goal and he slotted past Morgan De Sanctis.
Still missing injured forward Ezequiel Lavezzi, Napoli left new signing Eduardo Vargas out of the side and fielded Goran Pandev alongside Marek Hamsik and Uruguay forward Cavani in attack.
They created plenty of openings but needed a highly controversial incident to grab the equaliser.
Napoli were originally awarded a free-kick just outside the area for handball but the referee then changed his mind after consulting with the linesman and gave a penalty.
Cavani step up to convert for his 16th goal of the season in all competitions in the 71st minute amid angry Bologna protests.
Napoli, whose results have varied between a 3-1 win over AC Milan and 6-1 drubbing of Genoa to a 2-1 home defeat by Parma, are sixth with 28 points from 18 games. Bologna are 16th with 19 points.