Can you give examples of kernel bugs that can be targeted on an otherwise locked down system? Let's say something running just LAMP and all other ports closed off with a software firewall. Even the one in this article seems very tricky to actually exploit.

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