Any vulnerabilities in any of your software that can talk to a network, ssh, browser, the operating system itsself could be exploited if your firewall is down
If you're using username and password and have ssh enabled, for example anyone on your network could attempt to log in to your machine
At that point why not just have the firewall set to deny everything just to be safe though? There's always the chance you missed something that's decided to listen on some random port and if you aren't using anything that listens on a network why have the firewall open anyway
Any vulnerabilities in any of your software that can talk to a network, ssh, browser, the operating system itsself could be exploited if your firewall is down
If you're using username and password and have ssh enabled, for example anyone on your network could attempt to log in to your machine
Let's just say the system does not have any outward facing service (no ssh, http, smb, nfs).
At that point why not just have the firewall set to deny everything just to be safe though? There's always the chance you missed something that's decided to listen on some random port and if you aren't using anything that listens on a network why have the firewall open anyway
For ssh, sure.
But a browser? No way.
My understanding is there can be a vulnerability in absolutely anything
Browsers are unlikely to but don't think it's impossible
A firewall protects open ports on your machine. A browser does not have any open ports.
Of course they have vulnerabilities, but a firewall won't protect you from them.