wp-02-0012: Carello 1.3 Remote File Execution (Updated 1/10/2002)

[Matt Moore <matt () westpoint ltd uk>]

Westpoint Security Advisory

Title:        Carello 1.3 Remote File Execution
Risk Rating:  High
Software:     Carello Shopping Cart
Platforms:    Win2k, WinNT
Vendor URL:   www.carelloweb.com
Author:       Matt Moore <matt () westpoint ltd uk>
Date:         10th July 2002
Advisory ID#: wp-02-0012
Revision:     Updated 22/02/2002 (see addendum)

Overview:
=========

Carello 1.3 is a web based shopping cart solution, which uses hidden 
HTML form
fields to specify executables to handle POSTed form data.

Details:
========

Remote File Execution
---------------------

Carello uses hidden form fields to specify the names of executables on 
the server which
are to handle POSTed form data. This allows an attacker to manipulate 
the HTML to
specify arbitrary executables, which the Carello server software will 
then run. For
example, a typical section of an HTML page created by Carello looks like 
(angle brackets
omitted):

form method="POST" action= "http://server/scripts/Carello/Carello.dll";
input type="hidden" name="CARELLOCODE" value="WESTPOINT"
input type="hidden" name="VBEXE" value= "c:\inetpub\..carello-exe-file"
input type=....etc etc

Hence, by specifying a value like ' 
c:\..\..\..\..\..\..\..\.\winnt\notepad.exe '
an attacker can execute arbitrary files.

Vendor response:
================
The vendor indicated that the vulnerability will be fixed in the next 
version
of Carello. When asked for an expected release date, they replied that:

'Unfortunately, we do not have a plan to upgrade the program so far. But 
I put
your indication on our program modification request list.'

This advisory is available online at:

http://www.westpoint.ltd.uk/advisories/wp-02-0012.txt

Addendum:
=========
22/02/2002 - New information.

Westpoint would like to thank Peter Grundl of KPMG for providing additional
information on this vulnerability:

Exploitable via GET requests
-----------------------------
The vulnerability can be exploited by making a GET request to the 
vulnerable .dll
and specifying the 'VBEXE' as a parameter.

Passing parameters to the invoked executable
----------------------------------------------
It is possible to pass parameters to the executables invoked using this 
vulnerability.

For example:

/scripts/Carello/Carello.dll?VBEXE= 
c:\.\winnt\system32\cmd.exe%20/c%20dir >c:\dir.txt

Carello attempts to verify that the VBEXE file specified is not in 
%systemroot% - prepending
\.\ to the path circumvents this restriction.