Our existing computing platforms are very specific and very limited. Without knowledge of that specific design and the accompanying limitations, how could you pre-craft a non-interactive "exploit" that could be executed by such a system? I do think that it becomes more possible if we have AGI-like systems doing detection and analysis, but we do not. In addition, any universal exploit against AGI systems would probably have to be universal enough to also affect human intelligence.
For a clearer example, there's a reason a virus that affects Windows doesn't affect Linux. Or a virus that affects Windows XP doesn't affect Windows 11. There are of course counter examples, but this is the trend. To understand why the counter examples exist requires expert knowledge (or rather that there are basically the same things running in the same way).
We are currently discussing exploits designs by foreign intelligences to infect artificially intelligent systems. We are not talking about privilege escalation on a Mac.
That's where you're confused. The only one insisting the topic under discussion is the infection of AI systems (as opposed to classical computing systems) is you...
There's a bit in one of Larry Niven's books, possibly Ringworld. The protagonists are worried about what novel aliens might do. Somebody proposes ducking into hyperspace, where tracking them is "theoretically impossible". Another character responds, "What if they use different theories?"
That something seems unlikely to a human used to dealing with other humans at the same or lower technology level to me says more about humans than about what's possible.
Reminds me of an episode of Stargate where they fire 'stealth' (invisible to radar) nukes at the Goa'uld ships, and they're just stood looking out the window at them! https://www.youtube.com/watch?v=JvBsXxNc7k8
Anyone who says anything like "it's impossible" etc just has a complete lack of imagination.
We've built enough stupid complexity* that either the aliens must already have spied it out completely (but if they done that they could likely overtake is in any way quickly..), or it just won't happen. (*)
I mean seriously, how would you design a virus in some limited signal that has a chance of overtaking any arbitrary specific system someone may have invented, that's impossible. Never say never maybe my imagination is too small..