The authentication method in Laravel 8.x through 9.x before 9.32.0 was discovered to be vulnerable to user enumeration via timeless timing attacks with HTTP/2 multiplexing. This is caused by the early return inside the hasValidCredentials method in the Illuminate\Auth\SessionGuard class when a user is found to not exist.
https://github.com/laravel/framework/releases/tag/v9.32.0
https://github.com/laravel/framework/pull/44069