It would depend on the laws of the jurisdiction. I would imagine if you can show you kept the firmware up to date and had a secure as possible config (eg not having admin interfaces exposed to the internet), you could argue that there's no negligence - outside of maybe using a known insecure vendor; sometimes I think that would be a good idea (cough cough Fortinet).

Germany has some sensible laws about personal responsibility, like it being an offence to run out of gas on the autobahn and seriously treating driving in general as a privilege. But it requires a certain cultural mindset.