CVE-2018-8940 in Cloud Contact Center Platform
Summary
by MITRE
ClientServiceConfigController.cs in Enghouse Cloud Contact Center Platform 7.2.5 has functionality for loading external XML files and parsing them, allowing an attacker to upload a malicious XML file and reference it in the URL of the application, forcing the application to load and parse the malicious XML file, aka an XXE issue.
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Analysis
by VulDB Data Team • 09/19/2023
The vulnerability identified as CVE-2018-8940 represents a critical server-side XML external entity injection flaw within the Enghouse Cloud Contact Center Platform version 7.2.5. This issue resides in the ClientServiceConfigController.cs component which handles external XML file loading and parsing functionality, creating an attack vector that allows remote exploitation without authentication requirements. The vulnerability stems from insufficient input validation and sanitization mechanisms when processing XML content, specifically failing to properly restrict external entity references during XML parsing operations. The flaw enables attackers to craft malicious XML documents that, when referenced through the application's URL parameter, trigger the platform to load and process these external entities, potentially leading to unauthorized data access, server-side request forgery, or even remote code execution depending on the underlying XML parser implementation and system configuration.
The technical exploitation of this XXE vulnerability follows a pattern consistent with CWE-611 (Improper Restriction of XML External Entity Reference) and aligns with ATT&CK technique T1213.002 (External Remote Services) and T1071.004 (Application Layer Protocol: DNS). Attackers can leverage this vulnerability by uploading specially crafted XML files containing malicious external entity declarations or by manipulating URL parameters to reference external XML resources hosted on attacker-controlled servers. The XML parser within the platform processes these entities without proper restrictions, allowing the system to fetch and execute content from external sources. This creates a pathway for information disclosure where sensitive data from the server's file system, internal network resources, or other system components can be accessed through carefully constructed XML payloads that exploit the parser's behavior.
The operational impact of this vulnerability extends beyond simple data exposure, potentially enabling attackers to perform server-side request forgery attacks that can target internal systems not directly exposed to the internet. The vulnerability affects the availability and integrity of the contact center platform by allowing unauthorized manipulation of system behavior through XML parsing. Organizations using this platform face significant risks including potential data breaches, service disruption, and compliance violations. The vulnerability is particularly concerning in enterprise environments where contact center platforms often handle sensitive customer information, business communications, and may be integrated with other critical systems. The attack surface is broad as the functionality exists for loading external XML files through URL parameters, making it accessible through multiple attack vectors including web interface manipulation and API endpoint exploitation.
Mitigation strategies for CVE-2018-8940 should focus on implementing proper XML parsing restrictions and input validation mechanisms. Organizations must disable external entity resolution in XML parsers and implement strict XML schema validation to prevent unauthorized entity references. The recommended approach includes configuring XML parsers to reject external entity declarations, implementing proper access controls for XML file upload functionality, and applying input sanitization measures that prevent malicious XML content from being processed. Security measures should also encompass network-level restrictions to prevent access to internal resources from the vulnerable application, and regular monitoring for suspicious XML parsing activities. The platform should be updated to a patched version that addresses the XXE vulnerability, with additional security controls such as web application firewalls and runtime application self-protection mechanisms to provide defense-in-depth. Organizations should also conduct thorough security assessments of all XML processing components and implement proper security training for developers to prevent similar vulnerabilities in future application development cycles.