CVE-2017-7457 in MX-AOPC Server
Summary
by MITRE
XML External Entity via ".AOP" files used by Moxa MX-AOPC Server 1.5 result in remote file disclosure.
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Analysis
by VulDB Data Team • 08/31/2020
The vulnerability identified as CVE-2017-7457 represents a critical security flaw in Moxa MX-AOPC Server version 1.5 that stems from improper handling of XML External Entity (XXE) requests within .AOP files. This vulnerability allows remote attackers to exploit the server's processing of external entity references, potentially enabling unauthorized access to sensitive files on the system. The issue manifests when the server processes .AOP files that contain XML content with external entity declarations, creating a pathway for attackers to retrieve arbitrary files from the target system through crafted XML payloads.
The technical implementation of this vulnerability leverages the XML parsing mechanisms within the Moxa MX-AOPC Server software, specifically targeting the server's handling of XML documents that reference external entities. When the server encounters an .AOP file containing malicious XML with external entity declarations, it fails to properly validate or restrict access to external resources, allowing the XML parser to resolve these references and potentially disclose system files. This flaw aligns with CWE-611, which categorizes improper restriction of XML external entity reference as a critical weakness in XML processing implementations. The vulnerability operates at the application layer, specifically affecting the server's XML parsing and file access controls, making it particularly dangerous in industrial control systems where the MX-AOPC Server is commonly deployed.
The operational impact of CVE-2017-7457 extends beyond simple file disclosure, as it can enable attackers to gain unauthorized access to sensitive system information, configuration files, and potentially escalate privileges within the industrial control environment. This vulnerability is particularly concerning in industrial IoT and SCADA systems where Moxa devices are frequently deployed, as it could allow attackers to extract critical operational data or gain insights into system architecture. The remote nature of the exploit means that attackers can leverage this vulnerability from outside the network perimeter, making it especially dangerous for organizations that do not properly segment their industrial networks. The vulnerability also aligns with ATT&CK technique T1071.004, which covers application layer protocol manipulation, and T1005, which involves data from local system storage, demonstrating how this vulnerability can be used to extract sensitive information from compromised systems.
Organizations affected by CVE-2017-7457 should immediately implement mitigations including patching the Moxa MX-AOPC Server to a version that properly validates XML content and restricts external entity references. Network segmentation and access controls should be strengthened to limit exposure of the affected servers to untrusted networks. Additionally, implementing XML parser configuration changes that disable external entity resolution and DTD processing can provide defense-in-depth measures against similar vulnerabilities. Regular security assessments of industrial control systems should include validation of XML processing capabilities to prevent similar XXE vulnerabilities from being exploited in other industrial equipment. The vulnerability also highlights the importance of secure coding practices in industrial software development, particularly regarding XML parsing and external resource handling, as defined by secure coding standards such as those outlined in the OWASP Secure Coding Practices and ISO/IEC 27034 for application security.