Security isn't a thing that can be secured in an absolute sense, only a relative one.
For example, while the catastrophic ineptitude of the Russian forces at the start of their invasion has caused me to believe 80% of their nukes don't work any more, even just one nuke detonated as a HAEMP would destroy a continental-sized power grid — and the same visible signs of corruption that gave me the previous 80%, that also means there's a substantial chance at least one of the warheads ended up on the black market.