A vulnerability exists in the test.php script of OmniHTTPd.  The script
makes a classic coding error -- trusting unsanitized user input.  The query
string and cookie values are returned unfiltered.  Of most concern, of
course, is the query string:

http://localhost/test.php?%3CSCRIPT%3Ealert%28document.URL%29%3C%2FSCRIPT%3E
=x

The impact of this vulnerability will vary by site.  A production site would
most likely *not* have the sample scripts installed, but it would be wise to
check.

"The reason the mainstream is thought
of as a stream is because it is
so shallow."
                     - Author Unknown

OmniHTTPd's Test.shtml sample is also vulnerable to a similar issue:

http://localhost/test.shtml?%3CSCRIPT%3Ealert(document.URL)%3C%2FSCRIPT%3E=x

Will pop up an alert containing the above URL.  Of course, this has other
uses (cookie theft, faking sources, etc.)

I've discovered another vulnerability in one of the OmniHTTPd sample apps.
This time, the culprit is "/cgi-bin/redir.exe".  This app is vulnerable to a
newline injection issue.  The vulnerability occurs because the "URL" query
parameter (case sensitive) is decoded and placed directly into the response
as the "Location" header.  If an attacker places urlencoded newlines
("%0D%0A") into the parameter, the headers following the "Location" header,
as well as the resultant entity, can be controlled.

I had a tough time exploiting this vulnerability to add headers, because
OmniHTTPd would not add my header. :-(  However, I was able to exploit this
vulnerability to produce the following output:

[Begin Server Response]
HTTP/1.0 302 Redirection
Content-Type: text/html
Date: Sun, 25 Aug 2002 16:36:39 GMT
Location: http://www.yahoo.com/
Server: OmniHTTPd/2.10

<script>alert(document.URL)</script>


[End Server Response]

This will pop up an alert, and then redirect to yahoo.com on browsers that
display redirect entities (IE will not work for this)

I was a bit puzzled by the "Server" header between the Location and the
entity, but I figured out that OmniHTTPd was inserting the header after CGI
processing was complete.

Exploit URL:

http://localhost/cgi-bin/redir.exe?URL=http%3A%2F%2Fwww%2Eyahoo%2Ecom%2F%0D%
0A%0D%0A%3CSCRIPT%3Ealert%28document%2EURL%29%3C%2FSCRIPT%3E

"The reason the mainstream is thought
of as a stream is because it is
so shallow."
                     - Author Unknown