I have cups (but not cups-browsed) installed, but I only start the service when I need to print something a few times a year. Until then it is only a binary sitting in a folder, nothing more.
Honestly it isn’t a big deal if you just use it on local host. Just make sure cups is sandboxes like it should be. (Systemd)
Yes, but exactly that was/is the issue of this bug. cups-browsed was attaching itself to every available IP on the system. And cups-browsed can’t only be bind to localhost, it would defeat the whole purpose of that tool. For it to be able to find other printers in the network it needs to be bound to a non-localhost-IP address. So, not much to sandbox
Oh, hey! Wasn’t even a problem for me.
Entirely personal recommendation, take it or leave it: I’ve seen and attacked enough of this codebase to remove any CUPS service, binary and library from any of my systems and never again use a UNIX system to print. I’m also removing every zeroconf / avahi / bonjour listener. You might consider doing the same.
Great advice. It would appear these developers don’t take security seriously.
Mdns is something most people have no idea exists.
Oh, neat, all my devices broadcast all their open ports, services, addresses, hardware and names? Cool!
No.
If your router/firewall is configured to let these broadcasts through you have a problem. If it is working correctly and you have an attacker on your lan? You have already lost.
It depends. If you’re using a laptop and say you take it to university or work then you’re not on your LAN. You’re on someone else’s LAN and they may have no interest in trying to stop these types of attacks via any kind of client isolation or it may be incomplete.
I can imagine it’s a very normal scenario for university students to have CUPS running and available on all networks as they may need to print at their university.
They’re standardised zeroconnf protocols. Apple was part of the early development.
Bonjour is the apple implementation for mDNS.
Avahi is the GPL compliant implementation.
mDNS, llmnr (ms developed), have been known for ages to be vulnerable.
https://en.m.wikipedia.org/wiki/Zero-configuration_networking#Standardization
*I don’t like apple
Worse than the exploit, is hearing the struggles the author faced to report it
Twenty-two days of arguments, condescension, several gaslighting attempts, more or less subtle personal attacks, dozens of emails and messages, more than 100 pages of text in total. Hours and hours and hours and hours and fucking hours. Not to mention somehow being judged by a big chunk of the infosec community with a tendency of talking and judging situations they simply don’t know.
I mean, OK, it’s a vulnerability and there are interesting implications, but this is hardly significant in any pracitcal sense of the word.
the potential victim has to run their system without a firewall, has to print to the printer they’ve never interacted with before and then the attacker can run shit with whatever the printing system’s user id is, which shouldn’t be an issue on any reasonably modern distro.
I routinely remove cups and friends from any system I run because I have no need for printing and it bothers me to see it constantly during every system upgrade.
