In a chaotic match where both semi-finalists fumed at the officials, Rublev was defaulted by the chair umpire for unsportsmanlike conduct.
Bublik, who clawed his way back from a set down to lead 6-7 (4-7) 7-6 (7-5) 6-5, was awarded the win.
Rublev makes his protests to ATP Supervisor Roland Herfel after the controversial incident. (AP PHOTO)
It was after he went 6-5 down in the third that the combustible Russian appeared to say something to the line judge.
ATP supervisor Roland Herfel came down to the court, accompanied by a Russian speaker, who claimed Rublev had sworn in his native language.
Rublev protested, insisting he was speaking in English, while Bublik also backed his opponent.
"I didn't say 'f******'. I swear to God. This is huge. I swear to God," said Rublev.
The offence would usually merit a warning in the first instance, but the 26-year-old was defaulted by umpire Miriam Bley amid jeers from the crowd in Dubai.
It was a controversial end to a tight match which ensured there would be no repeat of last year's final when Rublev lost to Daniil Medvedev.
The top seeded Medvedev will face fifth-seeded Frenchman Ugo Humbert in the other last-four clash later on Friday.
With PA
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