Sylius: Channel-based payment method restriction bypass on shop account orders API endpoint

Sylius is an Open Source eCommerce Framework on Symfony. Starting in version 2.0.0 and prior to version 2.0.18, 2.1.15, and 2.2.6, an authorization bypass vulnerability exists in the shop account API. The `PATCH /api/v2/shop/account/orders/{tokenValue}/payments/{paymentId}` endpoint, used by an authenticated shop customer to change the payment method of an order that has been placed but not yet paid (state `STATE_NEW`), does not validate that the chosen payment method is enabled for the order's channel. The equivalent checkout endpoint (`PATCH /api/v2/shop/orders/{tokenValue}/payments/{paymentId}`) correctly rejects out-of-channel payment methods with `HTTP 422`; the account endpoint silently accepts them and returns `HTTP 200`. An authenticated customer can therefore assign any globally enabled payment method to their own placed order, including methods that the store operator has explicitly excluded from that channel. The issue is fixed in versions: 2.0.18, 2.1.15, 2.2.6 and above. As a workaround, decorate the `Sylius\Bundle\ApiBundle\Changer\PaymentMethodChangerInterface` service in the application.

The application performs an authorisation check, but it does not correctly enforce the required permission boundary.

An attacker operating through a network path may attempt exploitation with low privileges. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.