There are plenty of out of support systems still in the wild and while I'm not arguing they are completely secure I was under the impression that kernel vulnerabilities generally make a minor exploit in something else worse (chained priv escalation for example) and generally are difficult to exploit on their own. If I'm mistaken I'd love to know
That includes the one port your LAMP stack uses.
Or, the attacker might be originating from the other side of a device, like within a LAN. Malicious employees/house guests/what-have-you could target devices from inside your network where most devices (not just servers) don't have as much protection and often have other open ports accessible, like file sharing/SMB, SSH, SMTP, RDP, databases etc.
How about forwarding a port for wireguard or ssh?
AFAIK all the backdoors which have been found in some models are only accessible from the LAN side, and if you have an attacker inside the network, it's already too late.
Disagree, I think it's still a good idea to try to mitigate e.g. root escalations via this bug from devices within your network as well, as they could become compromised at any moment via other means and then promote themselves to root.
It shouldn't be though. Just because my smart lightbulb has an RCE and is isolated on its own VLAN with the router doesn't mean it should be able to attack the router and escalate to access my devices on other VLANs. It should only be able to do damage limited within its own vlan.