The good news about nukes: they have a shelf life -- most soviet-era nukes needed to be replaced every 12 years, as the loss of fissile material to natural radioactive decay would render them dirty bombs after a certain point. Now don't get me wrong, a dirty bomb still sucks, but it's no nuke.
So when a collapsing Russia is hypothetically selling nukes, they're probably selling old depleted nukes or nearly expired nukes. To a terrorist it is almost the same thing, but to nation stations looking at MAD, it really isn't.
Meet one of my former D&D characters: Kronos, master of space and time (chronurgy wizard), accidentally turned himself into a grung while experimenting on frog familiars. Jokes that he is his own familiar now. Also has a frog familiar. Claims it is himself from another timeline. Campaign goal: to recover his lost powers. Secret: is delusional, or is he?