CVE-2026-31867 — craftcms/commerce

An Insecure Direct Object Reference (IDOR) vulnerability exists in Craft Commerce’s cart functionality that allows users to hijack any shopping cart by knowing or guessing its 32-character number. This vulnerability enables the takeover of shopping sessions and potential exposure of PII.

Vulnerability Details

Root Cause

The CartController accepts a user-supplied number parameter to load and modify shopping carts. No ownership validation is performed - the code only checks if the order exists and is incomplete, not whether the requester has authorization to access it.

// CartController.php:374-389 - actionLoadCart()
public function actionLoadCart(): ?Response
{
    $number = $this->request->getParam('number');

    if ($number === null) {
        return $this->asFailure(Craft::t('commerce', 'A cart number must be specified.'));
    }

    // No ownership check - returns any cart to any requester
    $cart = Order::find()->number($number)->isCompleted(false)->one();

    // Cart is loaded into attacker's session without authorization
    ...
}

// CartController.php:606-616 - _getCart()
$orderNumber = $this->request->getBodyParam('number');
if ($orderNumber) {
    // Same issue - no ownership validation
    $cart = Order::find()->number($orderNumber)->isCompleted(false)->one();
    // Returns cart to any requester who knows the number
}

Attack Scenario

Prerequisites

• Target Craft Commerce installation with active shopping carts
• Knowledge of a victim’s cart number (32-character hex string)

Cart Number Acquisition Vectors

1. Referrer Header Leakage: Cart URLs shared externally expose the number
2. Browser History: Accessible on shared/compromised devices
3. Proxy/WAF Logs: Cart numbers logged in URL parameters
4. Social Engineering: Support tickets, screenshots containing cart URLs
5. Brute Force: While impractical for random targeting, feasible for targeted attacks against recently-created carts