https://github.com/znc/znc/issues/1459
As covered, after recent system updates, ZNC runs for a time then suddenly segfaults, complaining of "stack smashing" attempts. This occurs with ZNC and with various -git versions, so the issue doesn't seem to be with ZNC itself.
The github user 0KiB managed to catch a list of package updates, after which the described issue is triggered. https://pastebin.com/7CdNc9Ny