source: http://www.securityfocus.com/bid/2024/info
 
The freeware guestbook package from freeware.webcom.se provides a web-based guestbook feature, using CGI. Some versions of this guestbook (undetermined at the time of writing) are vulnerable to an attack allowing an intruder to retrieve the contents of arbitrary files to which the web server has access. This can be accomplished by specifying the path and filename as the parameter "template" to either rguest.exe or wguest.exe - see Exploit for example. These two programs typically reside in /cgi-bin.

http://server/cgi-bin/rguest.exe?template=c:\winnt\system32\$winnt$.inf will return the $winnt$.inf file