CVE-2017-18357 in Shopware
Summary
by MITRE
Shopware before 5.3.4 has a PHP Object Instantiation issue via the sort parameter to the loadPreviewAction() method of the Shopware_Controllers_Backend_ProductStream controller, with resultant XXE via instantiation of a SimpleXMLElement object.
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Analysis
by VulDB Data Team • 08/10/2025
The vulnerability identified as CVE-2017-18357 represents a critical security flaw in Shopware versions prior to 5.3.4 that stems from improper input validation within the backend product stream controller. This issue manifests through the loadPreviewAction() method which accepts a sort parameter without adequate sanitization or validation, creating a pathway for malicious actors to manipulate the application's behavior through crafted input. The vulnerability specifically leverages PHP's object instantiation mechanisms to create a dangerous exploitation vector.
The technical exploitation occurs when an attacker submits a specially crafted sort parameter that triggers the instantiation of a SimpleXMLElement object within the application's processing flow. This particular object instantiation is vulnerable to external entity inclusion attacks, allowing attackers to inject malicious XML content that can be processed by the underlying PHP parser. The vulnerability classifies under CWE-611 Improper Restriction of XML External Entity Reference, which is a well-documented weakness in XML processing implementations that directly enables XXE attacks. The attack chain begins with the insecure parameter handling and culminates in the XML parser's ability to resolve external references, potentially enabling attackers to access local files, perform server-side request forgery, or even achieve remote code execution depending on the server configuration.
The operational impact of this vulnerability is severe for organizations running affected Shopware installations, as it provides attackers with a means to bypass normal access controls and potentially gain unauthorized access to sensitive system information. The vulnerability exists within the backend administration interface, making it particularly dangerous as it could allow attackers to escalate privileges and manipulate product data streams, potentially affecting inventory management, pricing information, and other critical business data. The XXE capabilities also enable attackers to perform reconnaissance activities by reading local files on the server, which could expose database credentials, application configuration files, or other sensitive information stored on the system.
Organizations should immediately implement the mitigations recommended by the Shopware development team, which primarily involves upgrading to version 5.3.4 or later where the vulnerability has been addressed through proper input validation and parameter sanitization. Additional protective measures include implementing web application firewalls that can detect and block suspicious XML content patterns, restricting external entity resolution in PHP XML parsers through configuration changes, and applying principle of least privilege access controls to backend interfaces. The vulnerability also highlights the importance of proper input validation and the need for security awareness in PHP application development, particularly when dealing with XML processing and object instantiation. Organizations should also consider implementing security monitoring and logging around backend administrative interfaces to detect anomalous behavior patterns that might indicate exploitation attempts. This vulnerability serves as a reminder of the critical importance of validating all user inputs and properly configuring XML parsers to prevent XXE attacks, which remain a prevalent threat in web application security landscapes.