CVE-2015-6318 in TelePresence Video Communication Server
Summary
by MITRE
Cisco TelePresence Video Communication Server (VCS) Expressway X8.5.1 and X8.5.2 allows local users to write to arbitrary files via an unspecified symlink attack, aka Bug ID CSCuv11969.
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Analysis
by VulDB Data Team • 06/20/2022
The vulnerability identified as CVE-2015-6318 affects Cisco TelePresence Video Communication Server (VCS) Expressway versions 8.5.1 and 8.5.2, representing a critical security flaw that enables local attackers to manipulate file system operations through symbolic link manipulation. This vulnerability resides within the file handling mechanisms of the VCS Expressway platform, which is designed to facilitate video communication services in enterprise environments. The issue stems from insufficient validation of symbolic link operations during file write processes, creating a pathway for unauthorized file system modifications that could compromise the integrity and confidentiality of the affected system.
The technical exploitation of this vulnerability involves a local attacker leveraging a symlink attack to redirect file write operations to arbitrary locations within the file system. When the VCS Expressway processes file operations, it fails to properly validate or sanitize symbolic link references, allowing an attacker to create malicious symbolic links that point to sensitive system files or directories. This flaw falls under the category of improper file system access control and can be classified as a weakness in the software's file handling routines. The vulnerability specifically manifests when the system attempts to write files, where the symbolic link resolution process does not adequately verify the target location, potentially enabling attackers to overwrite critical system files or inject malicious content into sensitive locations.
The operational impact of this vulnerability extends beyond simple file system manipulation, as it provides a potential foothold for more extensive attacks within the network infrastructure. Local attackers who can exploit this vulnerability gain the ability to modify system files, potentially leading to privilege escalation or service disruption. The VCS Expressway serves as a critical component in video communication networks, and compromise of this system could result in unauthorized access to video conferencing sessions, disruption of communication services, or even complete system takeover. This vulnerability particularly affects organizations relying on Cisco's video communication solutions, where the compromised system could serve as a pivot point for lateral movement within the network infrastructure.
Organizations should implement immediate mitigations including applying the vendor-provided security patches and updates released by Cisco to address this vulnerability. System administrators should also conduct thorough security assessments of the affected VCS Expressway installations, reviewing file permissions and implementing additional access controls to limit local user privileges. The vulnerability demonstrates the importance of proper input validation and secure file handling practices, aligning with security standards such as CWE-367, which addresses time-of-check to time-of-use (TOCTOU) race conditions. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation and persistence through file system manipulation, emphasizing the need for comprehensive security monitoring and access control measures. Additionally, organizations should consider implementing network segmentation and monitoring solutions to detect anomalous file system activities that might indicate exploitation attempts.