The South Korean scored his fifth goal in five games to win the game, slotting in after collecting Erik Lamela's pass.

Spurs were sloppy in their opening-game loss to Monaco but were better in an entertaining game in Russia and could have won by more.

Dele Alli also hit the crossbar with a fierce 20-yard strike.

Spurs, who travelled to Russia without Danny Rose, Eric Dier, Mousa Dembele, Moussa Sissoko and Harry Kane, had a couple of scares but deserved their win and can now head to face German side Bayer Leverkusen - who drew 1-1 at Monaco on Wednesday - with greater confidence.

Son shining

Son had a disappointing debut season for Spurs after joining the club in summer 2015 for a reported £22m from Leverkusen, scoring only eight goals in 41 appearances.

But he has hit the ground running this campaign, shouldering the goal-scoring burden for his side over the first few months with crucial strikes.

His input has become even more important as Harry Kane struggles for form and fitness and the England striker's current understudy Vincent Janssen strives to turn effort into impact.

Son followed up his two-goal displays in the league victories at Stoke and Middlesbrough with the winner on Tuesday - another neat finish that squirmed under the outstretched hand of home keeper Igor Akinfeev.

The 24-year-old could have made a hat-trick of braces for the season to ease Tottenham's nerves but after turning well in the box his shot was blocked.

Spurs learn quickly

The relief of the goal was clear to see in the Tottenham players, who had just started to show signs of frustration following 70 minutes during which they had plenty of possession but too often failed with their final ball or fired efforts off target.

In their opening game against Monaco they lacked concentration at the back and an inability to capitalise on chances at the other end, and there were echoes of this in Moscow.

As well as striking the bar, Alli also looped a header on to the roof of the net and failed to control a pass from deep after he had broken the offside trap.

Thankfully for the London side, CSKA do not possess Monaco's ruthless edge and wasted the good chances that came their way, Zoran Tosic twice curling shots wide of goal.

The Russians came back from two goals down to draw 2-2 at Leverkusen in their opening game, but they were managed well by Spurs after Son's goal to prevent another late rally.

Man of the match - Son Heung-min

What they said

Tottenham manager Mauricio Pochettino: "We've played much better tonight [than against Monaco] but it was a tough game as it's always difficult to play here in Moscow. It was very important for us to get three points here as we were in a must-win position.

"We're in the race for the next round. It's a very important three points. But there's four games remaining to play and everything is still open.

"It is very important that not only Harry [Kane], who was good before his injury and scored, that now another player has scored and that is very important for the team.

"I feel very pleased for Sonny {Son Heung-min]. He is on fire and to keep this form is very important for us."

CSKA Moscow manager Leonid Slutsky: "We knew Spurs would have a lot of possession, would dominate us in that part of the game.

"The goal was marginally offside, maybe yes, maybe no, we have to see it again, but it doesn't matter. In second half we tried to attack more but we didn't take our chances and that's why we are here."
The stats you need to know

    Spurs have been goalless in five of their past six Champions League games at half-time.
    CSKA have now conceded a goal in 24 successive CL matches, equalling the competition record by Spartak Moscow (2000-2006).
    Son Heung-min (Spurs, Bayer Leverkusen) became the second player from Asia after Park Ji-sung (PSV, Manchester United) to score for multiple sides in the Champions League.
    Lacina Traore has faced Spurs on four separate occasions - twice with Monaco, once with Anzhi Makhachkala and now with CSKA (D1 L3). He failed to get on the scoresheet in all three games.

What's next?

Tottenham host Premier League leaders Manchester City, who have yet to drop a point this season, at White Hart Lane on Sunday, 2 October at 14:15 BST.