CVE-2017-7907 in Wonderware Historian Client
Summary
by MITRE
An Improper XML Parser Configuration issue was discovered in Schneider Electric Wonderware Historian Client 2014 R2 SP1 and prior. An improperly restricted XML parser (with improper restriction of XML external entity reference, or XXE) may allow an attacker to enter malicious input through the application which could cause a denial of service or disclose file contents from a server or connected network.
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Analysis
by VulDB Data Team • 12/25/2020
The CVE-2017-7907 vulnerability represents a critical improper XML parser configuration flaw in Schneider Electric Wonderware Historian Client 2014 R2 SP1 and earlier versions. This vulnerability falls under the CWE-611 weakness category, specifically addressing improper restriction of XML external entity references, which is a well-documented security concern in web applications and data processing systems. The flaw exists within the XML parsing mechanism that processes data inputs from various sources, creating an attack surface where malicious actors can exploit the configuration to manipulate the application's behavior. The vulnerability is particularly concerning as it affects industrial control systems where data integrity and system availability are paramount for operational continuity.
The technical implementation of this vulnerability stems from the XML parser's failure to properly restrict external entity references during document processing. When the Wonderware Historian Client processes XML data, it does not adequately sanitize or validate the external entity declarations that may be embedded within the XML structure. This misconfiguration allows an attacker to craft specially formatted XML payloads that reference external resources or local files on the server. The parser, when processing these malformed inputs, can be coerced into performing unintended operations such as reading local files, accessing network resources, or consuming excessive system resources leading to denial of service conditions. The vulnerability essentially bypasses normal input validation mechanisms that should prevent such external references from being processed.
The operational impact of CVE-2017-7907 extends beyond simple denial of service scenarios to include potential data disclosure and system compromise within industrial environments. In the context of Wonderware Historian Client, which serves as a critical component for data collection, storage, and historical analysis in industrial automation systems, this vulnerability could lead to unauthorized access to sensitive operational data, configuration files, or system credentials. Attackers leveraging this XXE vulnerability could potentially extract database connection strings, user authentication details, or other confidential information stored within the system's file structure. The impact is particularly severe in industrial control environments where such data breaches could compromise the integrity of critical infrastructure operations and potentially lead to operational disruptions or safety hazards.
Mitigation strategies for CVE-2017-7907 should focus on implementing proper XML parser configuration and input validation controls. Organizations must ensure that XML parsers are configured to disable external entity resolution and DTD processing entirely, as recommended by the OWASP XML External Entity Prevention Cheat Sheet and aligned with ATT&CK technique T1213.1001 for data from external sources. The most effective remediation involves updating to Schneider Electric's patched versions of Wonderware Historian Client, as the vendor has addressed this specific XXE vulnerability in subsequent releases. Additionally, network segmentation and access controls should be implemented to limit exposure of the affected system, while application-level input validation should be strengthened to prevent malformed XML from reaching the parser. Security monitoring should include detection of unusual XML processing patterns and file access attempts that may indicate exploitation attempts, following ATT&CK technique T1070.004 for indicator of compromise detection and response activities.