The 37 year-old, not for the first time at the center of a judging storm, claimed the WBA super-middleweight for a third spell following a twelve round battle with the Russian.
Sturm gained a 115-113 verdict on two cards, whilst a third official saw it 114-114, although Chudinov has real claims for a trilogy contest.
With the debated win, Sturm banked a 40th career triumph, whilst Chudinov dropped a first reverse in fifteen bouts.
Two-time world heavyweight title challenger Francesco Pianeta proved too hot for Hasan Olaki to handle and was duly taken out in the fifth.
Italian Pianeta, who first lost to Wladimir Klitschko in 2013 before being halted in the very first round against Ruslan Chagaev in July, improved to 32-2-1 with his latest win.
Another ex-championship challenger, light-heavyweight Konni Konrad, also put himself back in the win column with a six round points win over Andrej Maurer.
Middleweight Ibrahim Guemues scored a third session win over Yesilat Berkta to keep up his one hundred percent stoppage record, whilst Alem Begic bagged and early finish in his contest opposite Leo Tchoula. Begic is now 12-0 as a pro.
Earlier, super middleweights Alex Born and Evgeny Shvedenko both carded decisions over their respective opponents over four and six rounds.
