Perhaps through the IndianaPWNS exploit it might be though. Whatever you do, do not upgrade to System Menu 4.2 as that removes homebrew.
Indiana Pwns works on system 4.2, as does stack smash. Bannerbomb has been disabled, but the Bannerbomb author says the fix is, and i quote "retarded", and a new version will be out shortly.
The Homebrew Channel team say a new installer will be released shortly.
So, don't upgrade to 4.2, but if you already have, or buy a new Wii with 4.2, all is not lost.