CVE-2020-24052 in EXVF5C-2
Summary
by MITRE
Several XML External Entity (XXE) vulnerabilities in the Moog EXO Series EXVF5C-2 and EXVP7C2-3 units allow remote unauthenticated users to read arbitrary files via a crafted Document Type Definition (DTD) in an XML request.
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Analysis
by VulDB Data Team • 08/22/2020
The CVE-2020-24052 vulnerability represents a critical XML External Entity processing flaw affecting Moog EXO Series EXVF5C-2 and EXVP7C2-3 industrial control units. This vulnerability falls under the CWE-611 category of Improper Restriction of XML External Entity Reference, which is a well-documented weakness in software systems that process XML data. The flaw enables remote attackers to exploit the system without authentication, making it particularly dangerous in industrial environments where operational technology systems are often exposed to untrusted networks. These devices are typically deployed in critical infrastructure settings including manufacturing plants, power generation facilities, and other industrial control systems where unauthorized access could lead to severe operational disruptions or safety hazards.
The technical implementation of this vulnerability occurs through the manipulation of Document Type Definition elements within XML requests processed by the affected Moog units. When the system receives a crafted XML payload containing a malicious DTD reference, it attempts to resolve external entities, allowing an attacker to read arbitrary files from the system's file system. This occurs because the XML parser lacks proper input validation and entity resolution restrictions, enabling attackers to leverage the XXE processing capabilities to access sensitive data. The vulnerability specifically targets the XML processing libraries used by these industrial devices, where the lack of proper sandboxing or entity restrictions creates an attack surface that can be exploited through standard network-based attacks.
The operational impact of CVE-2020-24052 extends beyond simple data exfiltration, as it represents a significant compromise of industrial control system security. Attackers could potentially access configuration files, system logs, authentication credentials, and other sensitive operational data that could be used for further exploitation or to understand the operational environment. In industrial settings, this could lead to unauthorized modification of control parameters, disruption of production processes, or even physical safety hazards if critical control systems are compromised. The vulnerability's remote nature means that attackers can exploit it from outside the network perimeter, making traditional network segmentation controls ineffective against this specific threat vector.
Mitigation strategies for CVE-2020-24052 should focus on implementing proper XML parser configuration and input validation controls. Organizations should disable external entity resolution in all XML processing components and implement strict input validation to prevent malicious DTD references from being processed. The recommended approach aligns with the ATT&CK framework's mitigation strategies for XXE attacks, particularly focusing on input validation and parser configuration controls. Additionally, network segmentation should be implemented to isolate critical industrial control systems, and regular security assessments should be conducted to identify and remediate similar vulnerabilities. Device vendors should provide firmware updates addressing this vulnerability, and organizations should establish robust patch management processes to ensure timely deployment of security fixes across their industrial control infrastructure.