SRC-2016-0009 : ATutor LMS password_reminder TOCTOU Authentication Bypass Vulnerability



CVSS Score:

7.5, (AV:N/AC:L/Au:N/C:P/I:P/A:P)

Affected Vendors:


Affected Products:

ATutor 2.2.1 is confirmed, other versions may also be affected.

Vulnerability Details:

This vulnerability allows remote attackers to execute arbitrary code on vulnerable installations of ATutor. Authentication is required to exploit this vulnerability however authentication bypass vulnerabilities are known and remote registration is open by default.

The specific flaw exists in the ‘password_reminder.php’ script when performing a password reset. The code attempts to perform a sanity check on the current session array after a new session has already been created. This can allow an attacker to bypass the check and reset a members password. An attacker can combine this with other vulnerabilities to achieve remote code execution.

Vendor Response:

ATutor has issued an update to correct this vulnerability. More details can be found at:

Disclosure Timeline:

  • 2016-03-17 – Vulnerability reported to vendor
  • 2016-03-17 – Vendor confirmed issue
  • 2016-03-19 – Vendor releases a patch
  • 2016-03-19 – Coordinated public release of advisory

Proof of Concept:


This vulnerability was discovered by Steven Seeley of Source Incite