A vulnerability in the web front-end of Brother printers (called Debut) allows an attacker to launch a Denial of Service attack. The attack is executed by sending a single malformed HTTP POST request. The attacker will receive a 500 error code in response, the web server is rendered inaccessible and all printing will cease to function. This vulnerability appears to affect all Brother printers with the Debut web front-end.
Unfortunately, despite multiple attempts to contact Brother about this issue, no patch appears to be pending. In order to mitigate this issue, admins are left to their own devices. Strict access control is in order here and using a firewall or similar device to restrict web access to only those admins that need it will help to mitigate the threat here. Unfortunately, poor access control is all too common. In fact there were a little over 16,000 vulnerable devices accessible from the Internet at the time of this writing.
Some people dismiss Denial of Service attacks as a mere nuisance, but they can tie up resources and reduce productivity at any organization. They can also be used as a part of an in-person attack on a organization. For instance, an attacker can launch a Denial of Service like this one and then show up at the organization as the "technician" called to fix the problem. Impersonating a technician would allow the attacker direct physical access to IT resources that they might never have been able to access remotely.
You can read the full advisory, including Proof of Concept, here: https://www.trustwave.com/en-us/resources/security-resources/security-advisories/?fid=18730