CVE-2026-31821

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

declare(strict_types=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

# config/services.yaml

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

    sylius_api.command_handler.cart.add_item_to_cart:
        class: App\CommandHandler\Cart\AddItemToCartHandler
        arguments:
            $orderRepository: '@sylius.repository.order'
            $productVariantRepository: '@sylius.repository.product_variant'
            $orderModifier: '@sylius.modifier.order'
            $cartItemFactory: '@sylius.factory.order_item'
            $orderItemQuantityModifier: '@sylius.modifier.order_item_quantity'
            $userContext: '@Sylius\Bundle\ApiBundle\Context\UserContextInterface'
        tags:
            - { name: messenger.message_handler, bus: sylius.command_bus }

Step 3. Clear cache

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 [email protected]

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

The application does not perform an authorization check before performing a sensitive operation. Typical impact: unauthorized access to restricted functionality or data.

Kodem intelligence

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

1. What is CVE-2026-31821? CVE-2026-31821 is a medium-severity missing authorization vulnerability in sylius/sylius (composer), affecting versions >= 2.0.0, <= 2.0.15. It is fixed in 2.0.16, 2.1.12, 2.2.3. The application does not perform an authorization check before performing a sensitive operation.
2. Which versions of sylius/sylius are affected by CVE-2026-31821? sylius/sylius (composer) versions >= 2.0.0, <= 2.0.15 is affected.
3. Is there a fix for CVE-2026-31821? Yes. CVE-2026-31821 is fixed in 2.0.16, 2.1.12, 2.2.3. Upgrade to this version or later.
4. Is CVE-2026-31821 exploitable, and should I be worried? Whether CVE-2026-31821 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
5. What actually determines whether CVE-2026-31821 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
6. How do I fix CVE-2026-31821?
   • Upgrade sylius/sylius to 2.0.16 or later
   • Upgrade sylius/sylius to 2.1.12 or later
   • Upgrade sylius/sylius to 2.2.3 or later