Of the former Soviet republics, only Russia has declared itself a Nuclear Weapon State.
If either Kazakhstan or Ukraine had nuclear weapons they would be violating the treaty. While we are all adults here and realize that sometimes countries violate treaties they sign, in this case it seems very unlikely.
Wouldn’t one or two of those former Soviet republics have the facilities and the scientists to whore one out to the terrorists? The number of bombs Ukraine had until 1996 was huge- about 5000 units or so.