The La Liga giants confirmed the players that will fly to Russia for their second match of this season’s competition on Sunday, with Julen Lopetegui omitting both Ramos and Bale from his 20-man travelling party after they picked up injuries in Saturday's scoreless derby draw against Atletico Madrid.
Spain international Ramos sustained a cut during a clash of heads with Saul Niguez early in proceedings, although he recovered to see out the contest.
Bale's fitness is of greater concern, with the Wales winger forced off at half-time with a suspected thigh injury.
Meanwhile, left-back Marcelo and in-form Isco missed the first Madrid derby of the campaign and have again been ruled out as they recover from a respective calf injury and appendicitis.
The loss of Bale is a significant blow for the Blancos, who are struggling in front of goal this season after the summer departure of Cristiano Ronaldo. Saturday’s stalemate at the Santiago Bernabeu was the second consecutive game in which they have failed to register a single goal, following a 3-0 defeat to Sevilla in midweek.
The Welshman was Madrid’s most prominent attacker in both ties and has three goals to his name so far this season.
His injury leaves the attacking options at Lopetegui’s disposal further depleted, with Isco’s appendicitis expected to keep him sidelined for a month.
The likes of Marco Asensio, Dani Ceballos and Mariano Diaz are among those likely to be called on to cover for the injured attacking pair on Tuesday.
Real’s Champions League campaign got off to a positive start earlier in September, with the 13-time winners beating Roma 3-0 in Group G opener.
Madrid sit top of the group on three points, with CSKA in second after a 2-2 away draw with Viktoria Plzen.