If you’re reading this you’re that means you don’t need further introduction to the problem, let go straight to solution then ;).
You will need some kind of firmware, apparently you can use official Buffalo firmware, official buffalo PRO (dd-wrt branded) firmware or just regular dd-wrt release. I used the first one - in my case wzrhpg300nh-176 (then you will be able to upgrade as usual, but for now let just get this one working again). Also you will need some kind of switch/another router, so you could connect both your PC and your bricked Buffalo to the same network.
Install the enhanced version of TFTP (
sudo apt-get install tftp-hpa). Turn off you router. Setup static IP on your PC to of 192.168.11.2 / 255.255.255.0 Gateway: 192.168.11.1.
cdto the directory where you downloaded&unpacked new firmware. Type
sudo arp -s 192.168.11.1 02-AA-BB-CC-DD-1A(you can use real MAC address of your router, but fake one should work just fine).
Now it’s time for TFTP:
tftp 192.168.11.1 tftp> verbose tftp> binary tftp> trace tftp> rexmt 1 tftp> timeout 60 tftp> put wzrhpg300nh-176 # this is the filename of downloaded firmware
Power up your router and wait for tftp to do it’s magic. After a while you should start seeing some progress and shortly after it should be transferred to the router.
Give it about 6 minutes to boot up. With a little bit of luck your router should be alive again.
More references: 1, 2. Good luck!