CVE-2015-4318 in TelePresence Video Communication Server
Summary
by MITRE
Cisco TelePresence Video Communication Server (VCS) Expressway X8.5.2 allows remote attackers to cause a denial of service via invalid variables in a GET request, aka Bug ID CSCuv40528.
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Analysis
by VulDB Data Team • 06/12/2022
The vulnerability identified as CVE-2015-4318 affects Cisco TelePresence Video Communication Server (VCS) Expressway version 8.5.2, representing a critical denial of service flaw that can be exploited by remote attackers without authentication. This vulnerability resides within the web server component of the VCS Expressway system, specifically in how it processes incoming HTTP GET requests containing malformed or invalid variables. The issue stems from insufficient input validation mechanisms that fail to properly sanitize and validate the parameters submitted in HTTP requests, creating a pathway for malicious actors to disrupt the normal operation of the communication server.
The technical exploitation of this vulnerability occurs when an attacker crafts a specially formatted GET request containing invalid variables or malformed parameters that the VCS Expressway system cannot properly handle. The system's web server component lacks robust error handling and input validation routines that would normally reject or sanitize such malformed requests before they can cause system instability. When the vulnerable system processes these invalid variables, it triggers an unexpected behavior that leads to service disruption, effectively causing a denial of service condition that prevents legitimate users from accessing the video communication services. This flaw operates at the application layer and can be classified under CWE-20, which represents "Improper Input Validation" in the Common Weakness Enumeration catalog, specifically addressing weaknesses in input validation that can lead to various security issues including denial of service.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the entire video communication infrastructure that relies on the VCS Expressway for connectivity and communication services. Organizations using this vulnerable version of Cisco VCS Expressway may experience complete loss of video conferencing capabilities, which can severely impact business continuity and collaborative operations. The remote nature of the attack means that threat actors can exploit this vulnerability from anywhere on the internet without requiring physical access or local network presence, making it particularly dangerous for organizations that depend on secure video communication for critical business functions. This vulnerability can be particularly impactful in enterprise environments where video conferencing systems are integral to daily operations and where the availability of communication services directly affects productivity and customer service delivery.
Mitigation strategies for CVE-2015-4318 should prioritize immediate patching of the affected Cisco VCS Expressway systems to the latest available software releases that contain the necessary security fixes. Organizations should also implement network-level protections including firewall rules that restrict access to the VCS Expressway web server ports and implement intrusion detection systems that can identify and alert on suspicious GET request patterns. Additionally, network segmentation should be employed to isolate the VCS Expressway systems from critical business networks, reducing the potential impact of successful exploitation. The vulnerability aligns with ATT&CK technique T1499.004 which covers "Endpoint Denial of Service" and represents a classic example of how insufficient input validation can create opportunities for attackers to disrupt system availability. Organizations should also consider implementing web application firewalls that can filter out malformed HTTP requests and provide additional layers of protection against similar vulnerabilities in the future. Regular security assessments and vulnerability scanning should be conducted to identify and remediate similar weaknesses in the broader network infrastructure that might provide alternative attack vectors for compromising communication systems.