The Laravel Encrypter component is susceptible to a vulnerability that may result in decryption failure, leading to an unexpected return of false. Exploiting this issue requires the attacker to manipulate the encrypted payload before decryption. When combined with weak type comparisons in the application's code, such as the example below:

<?php

$decyptedValue = decrypt($secret);

if ($decryptedValue == '') {
    // Code is run even though decrypted value is false...
}

References

• laravel/framework@28e53f2
• laravel/framework@886d261
• https://github.com/FriendsOfPHP/security-advisories/blob/master/laravel/framework/2018-03-30-1.yaml
• https://medium.com/@taylorotwell/laravel-security-release-5-6-15-and-5-5-40-56f1257933a0