Summary

A logic error in Admidio's two-factor authentication reset inverts the authorization check. Non-admin users cannot remove their own TOTP configuration, but they can remove other users' TOTP, including administrators. A group leader with profile edit rights on an admin account can strip that admin's 2FA.

Details

In modules/profile/two_factor_authentication.php at line 84, the authorization check uses an inverted condition:

// modules/profile/two_factor_authentication.php line 84
if (!($gCurrentUser->isAdministrator() || $gCurrentUserId !== $userId))
{
    throw new AdmException('SYS_NO_RIGHTS');
}

By De Morgan's law, this condition evaluates as:

• Blocks when: NOT isAdministrator() AND $gCurrentUserId === $userId
• In practice: blocks non-admins from resetting their OWN 2FA
• Passes: non-admins resetting OTHER users' 2FA (the opposite of the intended behavior)

The intended logic should block non-admins from resetting other users' 2FA. The !== operator on line 84 should be ===.

A group leader who holds hasRightEditProfile() permission on an admin user (checked earlier in the flow) can exploit this to strip 2FA from administrator accounts, reducing their security to password-only authentication.

Proof of Concept

1. As testuser (a non-admin group leader with edit rights on admin profiles), send:

POST /adm_program/modules/profile/two_factor_authentication.php HTTP/1.1
Content-Type: application/x-www-form-urlencoded
Cookie: ADMIDIO_..._SESSION_ID=<testuser_session>

mode=reset&user_uuid=<admin_user_uuid>

Result: the server removes 2FA from the admin account.

2. As testuser, attempt to reset their own 2FA:

POST /adm_program/modules/profile/two_factor_authentication.php HTTP/1.1
Content-Type: application/x-www-form-urlencoded
Cookie: ADMIDIO_..._SESSION_ID=<testuser_session>

mode=reset&user_uuid=<testuser_user_uuid>

Result: SYS_NO_RIGHTS error. The user cannot reset their own 2FA.

This confirms the authorization logic is inverted.

Impact

A group leader (or any user with profile edit rights on an admin) can disable two-factor authentication on administrator accounts. This degrades admin account security to password-only, opening the door to credential stuffing or brute force attacks without a 2FA barrier.

Recommended Fix

Change !== to === on line 84 of modules/profile/two_factor_authentication.php:

// Fixed condition: block non-admins from resetting OTHER users' 2FA
if (!($gCurrentUser->isAdministrator() || $gCurrentUserId === $userId))
{
    throw new AdmException('SYS_NO_RIGHTS');
}

Found by aisafe.io

References

• GHSA-rh3w-4ccx-prf9