CVE-2015-4327 in TelePresence Video Communication Server
Summary
by MITRE
The CLI in Cisco TelePresence Video Communication Server (VCS) Expressway X8.5.2 allows local users to obtain root privileges by writing script arguments to an unspecified file, aka Bug ID CSCuv12542.
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Analysis
by VulDB Data Team • 06/12/2022
The vulnerability described in CVE-2015-4327 represents a critical privilege escalation flaw within Cisco TelePresence Video Communication Server VCS Expressway version 8.5.2. This issue affects the command line interface component that governs system administration functions, creating a pathway for local attackers to gain elevated system privileges. The vulnerability specifically manifests when the system processes script arguments through an unspecified file writing mechanism, allowing malicious actors with local access to manipulate system-level operations. This type of flaw falls under the category of privilege escalation vulnerabilities, which are particularly dangerous as they enable attackers to bypass normal access controls and execute arbitrary code with the highest system privileges.
The technical implementation of this vulnerability involves the insecure handling of script arguments within the VCS CLI environment. When legitimate users execute commands through the interface, the system writes certain argument values to a file that should normally be protected from unauthorized modification. However, due to inadequate input validation and file access controls, local users can manipulate this process to inject malicious code or commands into the file. This file writing operation effectively becomes a vector for privilege escalation, as the system subsequently executes the malicious content with root privileges. The vulnerability demonstrates poor security practices in file handling and privilege management, where the system fails to properly sanitize inputs or enforce appropriate access controls during script execution.
The operational impact of this vulnerability is severe for organizations relying on Cisco VCS Expressway systems, as it provides a direct path to complete system compromise. Local attackers who can access the system through legitimate means such as user accounts or physical access can leverage this flaw to gain root access, potentially leading to complete system takeover. Once escalated to root privileges, attackers can modify system configurations, install backdoors, steal sensitive data, or disable security controls entirely. The vulnerability particularly affects environments where multiple users have local access to the system, as any user with basic login credentials could exploit this flaw. This makes it especially dangerous in enterprise settings where system administrators may not be fully aware of the potential for such local privilege escalation attacks.
Organizations should implement multiple layers of mitigation strategies to address this vulnerability effectively. Immediate patching of the affected VCS Expressway software to the latest available versions is the primary recommendation, as Cisco has likely released security updates to address this specific flaw. Additionally, implementing strict access controls and limiting local user accounts to only necessary privileges can reduce the attack surface. Network segmentation and monitoring of system access logs can help detect unauthorized attempts to exploit this vulnerability. The vulnerability aligns with CWE-276, which describes improper file permissions, and relates to ATT&CK technique T1068, privilege escalation through local exploitation. System administrators should also consider implementing file integrity monitoring solutions that can detect unauthorized modifications to critical system files, and regularly review system configurations to ensure proper privilege separation and access controls are maintained across all administrative interfaces.