There was a well known crypto weakness, CVE-2025-52464, that allowed man in the middle decryption of meshtastic traffic. It was fixed by a firmware patch that improved crypto discipline.

Bad randomness in generating keys, for anyone else wondering

From what I understand no, the relay node has no access to the messages.

If you compromise sending or receiving node then sure, of course.

Why bother? Just jam the fucking hell out of it. Most critical infrastructure is not on the ISM bands.

A lot of things are.

You could theoretically even shut down airplane printers in the cockpit if the jamming was strong enough.

You'd be surprised the things that are tied to ism wifi and bluetooth