CVE-2026-31821: Sylius is Missing Authorization in API v2 Add Item Endpoint

Impact The POST /api/v2/shop/orders/{tokenValue}/items endpoint does not verify cart ownership. An unauthenticated attacker can add items to other registered customers' carts by knowing the cart tokenValue.

POST /api/v2/shop/orders/{tokenValue}/items

Other mutation endpoints (PUT, PATCH, DELETE) are not affected. API Platform loads the Order entity through the state provider for these operations, which triggers VisitorBasedExtension and returns 404 for unauthorized users.

An attacker who obtains a cart tokenValue can add arbitrary items to another customer's cart. The endpoint returns the full cart representation in the response (HTTP 201), potentially leaking:

- Customer email address - Cart contents (products, quantities, prices) - Address data (billing and shipping if set) - Payment and shipment IDs - Order totals and tax breakdown - Checkout state

Patches The issue is fixed in versions: 2.0.16, 2.1.12, 2.2.3, and above.

Workarounds Add an ownership check in AddItemToCartHandler by injecting UserContextInterface and verifying the current user matches the cart owner before adding items.

Step 1. Patch the handler

Create new src/CommandHandler/Cart/AddItemToCartHandler.php:

php <?php

declare(stricttypes=1);

namespace App\CommandHandler\Cart;

use Sylius\Bundle\ApiBundle\Command\Cart\AddItemToCart; use Sylius\Bundle\ApiBundle\Context\UserContextInterface; use Sylius\Component\Core\Factory\CartItemFactoryInterface; use Sylius\Component\Core\Model\OrderInterface; use Sylius\Component\Core\Model\OrderItemInterface; use Sylius\Component\Core\Model\ProductVariantInterface; use Sylius\Component\Core\Model\ShopUserInterface; use Sylius\Component\Core\Repository\OrderRepositoryInterface; use Sylius\Component\Core\Repository\ProductVariantRepositoryInterface; use Sylius\Component\Order\Modifier\OrderItemQuantityModifierInterface; use Sylius\Component\Order\Modifier\OrderModifierInterface; use Symfony\Component\HttpKernel\Exception\NotFoundHttpException; use Symfony\Component\Messenger\Attribute\AsMessageHandler;

#[AsMessageHandler] final readonly class AddItemToCartHandler { public function construct( private OrderRepositoryInterface $orderRepository, private ProductVariantRepositoryInterface $productVariantRepository, private OrderModifierInterface $orderModifier, private CartItemFactoryInterface $cartItemFactory, private OrderItemQuantityModifierInterface $orderItemQuantityModifier, private UserContextInterface $userContext, ) { }

public function invoke(AddItemToCart $addItemToCart): OrderInterface { / @var ProductVariantInterface|null $productVariant / $productVariant = $this->productVariantRepository->findOneBy(['code' => $addItemToCart->productVariantCode]);

if ($productVariant === null) { throw new \InvalidArgumentException('Product variant with given code has not been found.'); }

/ @var OrderInterface|null $cart / $cart = $this->orderRepository->findCartByTokenValue($addItemToCart->orderTokenValue);

if ($cart === null) { throw new \InvalidArgumentException('Cart with given token has not been found.'); }

$this->assertCartAccessible($cart);

/ @var OrderItemInterface $cartItem / $cartItem = $this->cartItemFactory->createNew(); $cartItem->setVariant($productVariant);

$this->orderItemQuantityModifier->modify($cartItem, $addItemToCart->quantity); $this->orderModifier->addToOrder($cart, $cartItem);

return $cart; }

private function assertCartAccessible(OrderInterface $cart): void { if ($cart->isCreatedByGuest()) { return; }

$cartCustomer = $cart->getCustomer();

if (null === $cartCustomer || null === $cartCustomer->getUser()) { return; }

$currentUser = $this->userContext->getUser();

if ( $currentUser instanceof ShopUserInterface && $currentUser->getCustomer()?->getId() === $cartCustomer->getId() ) { return; }

throw new NotFoundHttpException('Cart not found.'); } }

Step 2. Override the service

diff config/services.yaml

services: App\: resource: '../src/' - exclude: '../src/{Entity,Kernel.php}' + exclude: '../src/{Entity,Kernel.php,CommandHandler}'

syliusapi.commandhandler.cart.additemtocart: class: App\CommandHandler\Cart\AddItemToCartHandler arguments: $orderRepository: '@sylius.repository.order' $productVariantRepository: '@sylius.repository.productvariant' $orderModifier: '@sylius.modifier.order' $cartItemFactory: '@sylius.factory.orderitem' $orderItemQuantityModifier: '@sylius.modifier.orderitemquantity' $userContext: '@Sylius\Bundle\ApiBundle\Context\UserContextInterface' tags: - { name: messenger.messagehandler, bus: sylius.commandbus }

Step 3. Clear cache

bash bin/console cache:clear

Reporters

We would like to extend our gratitude to the following individuals for their detailed reporting and responsible disclosure of this vulnerability: - @rokorolov

For more information If you have any questions or comments about this advisory:

- Open an issue in Sylius issues - Email us at security@sylius.com