At work, I use Cisco gear everywhere. Recently the SmartInstall Hack has become a security concern. There is a vulnerability in the SmartInstall system that allows bad actors to send arbitrary commands to your network infrastructure.

So I started out knowing how my network is shaped, that I customarily keep the 10-net IP space organized by state, then by city, and then finally by kind of equipment. Out of the four octets, the first one has to be 10, the second one is the state, and the next is the city in that state, and finally, I prefer to keep all my infrastructure gear between 250 and 254.

I started with nmap because I wanted a memory refresher so that I wouldn’t miss a device.

nmap 10.1-10.1-10.250-254

This command provides me a handy report of all the places on the inside of my network where ssh or telnet (depending on the age of the gear) reside. I print off the list, and it becomes an authoritative checklist for all my infrastructure gear.

Then one at a time, either ssh or telnet into the infrastructure devices and issue these commands in one paste command:

conf t
no vstack
end
wr mem

I don’t care if the command fails, it’ll write NVRAM to Flash either way which suits me fine. Once I was sure I got all the equipment that could be affected, I know that at least for this vulnerability, we’re all done. There won’t be anything, at least for this, at work for me to worry over.

Now if you use vstack or SmartInstall, your mileage may vary, but I certainly don’t use it. The default is to leave it on, so the smart money is in forcing it off. Why leave it open as a vulnerability if you don’t have any chance of bad actors on your LAN? Because it is one less thing to worry over.