Several media profiles on Vindman and even
Military Wikia claim he speaks fluent Russian and Ukrainian. That's probably what he himself told everyone. And it's what probably helped him to get that position, too.
But my Ukrainian sources who saw his interviews on local TV tell me he can't say a word in Ukrainian, and even his Russian is very basic.
As a child he was brought to the Russian-speaking Brighton Beach from Ukraine by his Russian-speaking parents. Like so many immigrant kids I've met, who had no special linguistic talents, he mostly spoke English at school and with his friends, and only some limited Russian at home. No one used Ukrainian where he lived, and there was no conceivable way he could've picked up that language, let alone become fluent.
A full disclaimer: coming from Ukraine myself, I speak and write fluent Russian. Since no one around me speaks Ukrainian, I had lost some of the former fluency, but I easily restored it after a couple of days when I visited Ukraine five years ago, and I can do it again the next time I'm there. Vindman has visited Ukraine many times and picked up zero Ukrainian. In other words, he is a liar. I'd really like to see the resumes Vindman had submitted in the course of his career, where he likely boasts of his fluency in two foreign languages.