7a69Adv#15 - Internet Explorer FTP command injection

From: Albert Puigsech Galicia (ripe_at_7a69ezine.org)
Date: 12/07/04

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    To: bugtraq@securityfocus.com
    Date: Tue, 7 Dec 2004 04:19:36 +0100

    - ------------------------------------------------------------------
           7a69ezine Advisories 7a69Adv#15
    - ------------------------------------------------------------------
      http://www.7a69ezine.org [05/12/2004]
    - ------------------------------------------------------------------

    Title: Internet Explorer FTP command injection

    Author: Albert Puigsech Galicia - <ripe@7a69ezine.org>

    Software: Microsoft Internet Explorer

    Versions: >= 6.0.2800.1106

    Remote: yes

    Exploit: yes

    Severity: Low-Medium

    - ------------------------------------------------------------------

    I. Introduction.

     Internet Explorer is a well-known HTTP browser, and like others it can use
    more protocols, for example FTP. The security historial of this navigator is
    really cool and we are glad for the excelent work done by Microsoft. We love
    your (in)security features.

    II. Description.

     In order to access to a server FTP using Internet Explorer you write
    "ftp://ftpuser:ftppass@server/directory" in the directions's bar and then the
    navigator connects to the server and executes the following commands (and
    other that have omitted because they are not important for this stuff).

       USER ftpuser
       PASS ftppass
       CWD /directory/

     The security problem resides in which is posible to inject FTP commands on
    the URL adding at the code %0a followed by your injected commands. If you do
    "ftp://ftpuser:ftppass@server/directory%0asomecommand%0a" it will execute
    those commands.

       USER ftpuser
       PASS ftppass
       CWD /directory

     The last line is an erroneous command, but it's not a problem because
    'somecommand' has already been executed.

    III. Exploit

     You need to deceive a user to go to your URL and then to introduce a valid
    user and password. So yes! The explotation also requires to apply social
    engineering. Then you can do a lot of things using this bug like create or
    delete files and directories, but probably, the most interesting thing is to
    download files. Its posible to do that using this URL;


     Then the server will connect to a.b.c.d and port e,f (see FTP RFC to
    translate the port number) and will send the file data.

    IV. Patch

     Internet Explorer sucks a lot, just turn to Firefox World.

    V. Timeline

    01/12/2004 - Bug discovered on konqueror browser
    03/12/2004 - Tried in IE. Also afected!
    05/12/2004 - Advisor released

    VI. Extra data

     You can find more 7a69ezine advisories on this following link:

        http://www.7a69ezine.org/avisos/propios [spanish info]


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