Sources close to the situation tell TMZ ... there's nothing serious going on between Kristin and Jeff Dye, and in fact -- we're told they've only hung out that one time they were seen in Chicago looking like a new couple.

Our sources say Kristin's just having fun right now and doesn't have -- nor is she looking for -- a boyfriend.

As for how Kristin and Jeff connected ... we're told he slid into her DMs a couple weeks ago, and they happened to be in Chi-town last week at the same time, so they met up.

You've seen the result, but it was just a night of good fun. Our sources say Kristin was enjoying a weekend of freedom -- it was her estranged hubby Jay Cutler's time with their kids.

As we've reported ... Kristin announced back in April she and Jay are getting divorced. Since then, things have gotten a little nasty ... with Kristin accusing him of "punishing" her financially, and Jay calling her expenses "frivolous."

Kristin insists there's no scandal involved with their divorce, though ... she says it just didn't work out.

So will it work out with Jeff? Probably too soon to tell, but if you're reading tea leaves ... we're told they haven't seen each other since the kiss.