With barely over a minute on the clock, Real were the architects of their own downfall, making a difficult away game in Russia all the more testing.
Toni Kroos attempted a long, volleyed pass, only to put it straight into the path of the striker, who is on loan at CSKA from Everton.
The Croatian bore down on goal, and there was nothing that Keylor Navas could do as he finished off the chance to put his side ahead.
It continues a miserable run for Julen Lopetegui in Russia - he was sacked by Spain on the ever of their World Cup campaign.