Coming together at 93 for two just before lunch, Ubarhande and Srivastava played with great purpose as Vidarbha reached 302 for two, still 317 runs behind the hosts.
Ubarhande and Srivastava were playing on 120 and 84 respectively when stumps were drawn for the day. They have racked up an unfinished 209 runs partnership for the third wicket so far.
Ubarhande has faced 243 balls and helped himself with 17 boundaries while Srivastava took 208 balls for his knock, which had 10 boundaries.
Karnataka, who desperately need an outright win for a chance to make it to the semis, went wicketless in the second session of as Ubarhande and Srivastava dug in.
The first session produced 72 runs in 29 overs and Vidarbha were 499 behind the hosts' first innings total of 619 for eight declared.
Resuming the day from the overnight score of 48 for no loss, Vidarbha soon lost Faiz Fazal, caught by Ganesh Satish off Abhimanyu Mithun for 22.
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Shiv Sundar Das, who played a sedate innings last evening, fell after he was snapped up by Manish Pandey off Stuart Binny for a well-made 53 runs off 136 balls with six boundaries.
With one day left in the game, Karnataka will seek to restrict Vidarbha to surpass an imposing first innings score of 619 for eight declared and not concede vital points to the visitors.