The SignUp & SignIn plugin for WordPress is vulnerable to Authentication Bypass via Weak Password Reset Validation leading to Account Takeover in versions up to, and including, 1.0.0. This is due to the pravel_change_password() AJAX handler — registered via wp_ajax_nopriv_pravel_change_password and therefore accessible to unauthenticated users — performing no nonce verification, no capability check, and only a loose equality check between an attacker-supplied reset_activation_code POST parameter and the target users forgot_email user meta value; when a user has never initiated a password reset, get_user_meta() returns an empty string that trivially satisfies this check against an omitted or empty attacker-supplied code. This makes it possible for unauthenticated attackers to change the password of any WordPress user, including administrators, by sending a crafted POST request to admin-ajax.php with action=pravel_change_password, reset_user_id set to the target accounts user ID, and new_password_custom set to an attacker-chosen password. Successful exploitation allows the attacker to authenticate with the newly set password and fully take over the targeted account, achieving administrator-level privilege escalation on the affected site.
Weakness
The product contains a mechanism for users to recover or change their passwords without knowing the original password, but the mechanism is weak.
Extended Description
It is common for an application to have a mechanism that provides a means for a user to gain access to their account in the event they forget their password. Very often the password recovery mechanism is weak, which has the effect of making it more likely that it would be possible for a person other than the legitimate system user to gain access to that user’s account. Weak password recovery schemes completely undermine a strong password authentication scheme. This weakness may be that the security question is too easy to guess or find an answer to (e.g. because the question is too common, or the answers can be found using social media). Or there might be an implementation weakness in the password recovery mechanism code that may for instance trick the system into e-mailing the new password to an e-mail account other than that of the user. There might be no throttling done on the rate of password resets so that a legitimate user can be denied service by an attacker if an attacker tries to recover their password in a rapid succession. The system may send the original password to the user rather than generating a new temporary password. In summary, password recovery functionality, if not carefully designed and implemented can often become the system’s weakest link that can be misused in a way that would allow an attacker to gain unauthorized access to the system.
Potential Mitigations
Related Attack Patterns
References
- https://plugins.trac.wordpress.org/browser/signup-signin/tags/1.0.0/lib/function.php#L222
- https://plugins.trac.wordpress.org/browser/signup-signin/tags/1.0.0/lib/function.php#L229
- https://plugins.trac.wordpress.org/browser/signup-signin/tags/1.0.0/lib/function.php#L38
- https://www.wordfence.com/threat-intel/vulnerabilities/id/c0a617fc-da3d-4828-b027-44093dd11769?source=cve