CVE-2015-4315 in TelePresence Video Communication Server
Summary
by MITRE
The Call Policy Configuration page in Cisco TelePresence Video Communication Server (VCS) Expressway X8.5.3 improperly validates external DTDs, which allows remote authenticated users to read arbitrary files or cause a denial of service via a crafted XML document, aka Bug ID CSCuv31853.
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Analysis
by VulDB Data Team • 06/12/2022
The vulnerability identified as CVE-2015-4315 affects Cisco TelePresence Video Communication Server (VCS) Expressway version 8.5.3 and represents a critical security flaw in the Call Policy Configuration page implementation. This vulnerability stems from improper validation of external Document Type Definitions (DTDs) within XML processing mechanisms, creating a pathway for malicious exploitation that can result in unauthorized data access or system disruption. The issue specifically manifests when the system processes crafted XML documents through its configuration interface, which is accessible to authenticated users with appropriate privileges.
The technical root cause of this vulnerability lies in the insecure handling of XML external entity references, which aligns with CWE-611 (Improper Restriction of XML External Entity Reference) and CWE-400 (Uncontrolled Resource Consumption). When the VCS Expressway processes XML documents containing malicious DTD declarations, it fails to properly restrict or validate external entity references, allowing attackers to craft XML payloads that can trigger various attack vectors. The vulnerability enables attackers to leverage XML External Entity (XXE) processing weaknesses to access arbitrary files on the system or cause denial of service conditions through resource exhaustion attacks.
The operational impact of this vulnerability extends beyond simple data theft, as it provides attackers with the capability to perform reconnaissance activities and potentially escalate privileges within the network environment. Remote authenticated users can exploit this weakness to read sensitive configuration files, system logs, or other confidential data stored on the VCS server. The denial of service component of this vulnerability can be particularly damaging in communication environments where video conferencing services are critical for business operations, potentially disrupting important meetings and collaborative activities. This vulnerability directly impacts the availability and confidentiality of the communication infrastructure, violating fundamental security principles of information assurance.
Organizations utilizing Cisco VCS Expressway products should implement immediate mitigations including applying the vendor-provided security patches and updates, configuring proper XML parsing restrictions, and implementing network segmentation controls to limit access to the Call Policy Configuration page. The ATT&CK framework categorizes this vulnerability under T1213 (Data from Information Repositories) and T1499 (Endpoint Denial of Service) techniques, emphasizing the need for both preventive and detective security controls. Additionally, implementing web application firewalls and XML validation rules can help detect and prevent malicious XML payloads from reaching the vulnerable system components, while regular security assessments and vulnerability scanning should be conducted to identify similar weaknesses in related network infrastructure components.