The news comes amid widespread reports the French works team Renault is set to pair current Toro Rosso driver Carlos Sainz with Nico Hulkenberg next year.
Kubica had been a contender for a 2018 seat after a spate of tests, but boss Cyril Abiteboul recently revealed his doubts.
“I don’t want to create speculation and I don’t want to put on the team some obligation to go further because there is an interest from the public to see Robert back,” said the Frenchman.
“We would all like Robert to be back, but it has to make sense,” Abiteboul added.
So with Sainz heading to Renault, the latest news is that Kubica has asked to be released from an agreement with the French team so he can explore other options for 2018.
Speed Week reports that those other options are Sauber and Williams.
Williams may be interested in the 32-year-old former BMW and Renault driver to replace Felipe Massa.
Mercedes-backed Pascal Wehrlein may have been another option for Williams next year, but because the British team is sponsored by alcohol brand Martini, teenager Lance Stroll’s teammate needs to be over the age of 25.
Amid all the Kubica rumours, there is one figure who is not barracking for the Pole’s comeback.
“Honestly, I don’t understand,” said 1997 world champion Jacques Villeneuve, whose own F1 career ended in 2006 when BMW replaced him with Kubica mid-season.
“Firstly, what driver is offered a return after six years?” he told the Belgian website F1nal-lap.
“Also, he was already struggling against Petrov at the end of his career. He won a race, like Maldonado did, but after that what? And then he is no longer 100 per cent.
“I think if he did not have his problem (injury), he would never have been given a second chance. What bothers me the most is that it’s a media thing, with plenty of other drivers more deserving of a second chance,” said Villeneuve.
Villeneuve, now a pundit for Italian TV, admits he has never got on with Kubica on a personal level — particularly during their shared time at BMW.
“At the time, he was unbearable,” said the French Canadian.
“For me, it was a terrible time. You know, in the paddock you have to be respectful. Respectful of what was achieved by others and the environment in which we operate.
“So I have a little trouble imagining something positive about his return to F1,” Villeneuve added.