The ex-Formula 1 driver had shown great pace on his European Rally Championship and World Rally Championship outings so far, but had struggled to turn that speed into results.
In Greece he dominated his division from the outset, and was as high as ninth overall before delayed top-class cars pushed him back to 11th.
"Finally after a disappointing time with my mistakes and car failures when we didn't manage to bring anything home, this is a great day. We have moved forward," said Kubica.
"These conditions were completely opposite to what I was used to for the last 20 years but we came here and performed in a good way."
Kubica emphasised that he still felt he was at the bottom of his development curve in rallying.
"I know I have to learn a lot and for sure over the next rallies I'll improve even more," he said.
"There is still a long way to go to the level I'd like to be."
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- European Rally Championship