CVE-2015-6261 in TelePresence Video Communication Server
Summary
by MITRE
Cisco TelePresence Video Communication Server (VCS) Expressway X8.5.2 allows remote authenticated users to bypass intended access restrictions and read configuration files by leveraging the Mobile and Remote Access (MRA) role and establishing a TFTP session, aka Bug ID CSCuv78531.
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Analysis
by VulDB Data Team • 06/13/2022
The vulnerability CVE-2015-6261 affects Cisco TelePresence Video Communication Server (VCS) Expressway version 8.5.2, representing a critical authorization bypass flaw that enables remote authenticated attackers to access sensitive configuration data. This issue specifically targets the Mobile and Remote Access (MRA) role functionality within the VCS system, where legitimate users with restricted privileges can exploit a design weakness to gain unauthorized access to system configuration files. The vulnerability stems from insufficient access controls during TFTP session establishment, allowing attackers to circumvent intended security boundaries that should protect sensitive operational data.
The technical implementation of this vulnerability involves the exploitation of a weakness in the TFTP protocol handling within the VCS Expressway environment. When users with MRA roles establish TFTP sessions, the system fails to properly validate access permissions, creating a pathway for privilege escalation. This flaw operates at the network communication layer where TFTP sessions are processed, enabling attackers to traverse normal access controls and retrieve configuration information that should remain restricted to authorized administrative personnel. The vulnerability specifically manifests when the system processes TFTP requests from authenticated users who possess MRA credentials, bypassing the standard authorization mechanisms that should prevent such access.
The operational impact of CVE-2015-6261 extends beyond simple information disclosure, as configuration files often contain sensitive data including user credentials, network settings, encryption keys, and system parameters that could be leveraged for further attacks. Attackers who successfully exploit this vulnerability can obtain detailed system information that may facilitate additional compromise attempts, including lateral movement within the network infrastructure, credential harvesting for privilege escalation, or targeted attacks against other systems that share similar configuration data. The exposure of configuration files can also reveal system architecture details that aid in planning more sophisticated attacks, potentially leading to complete system compromise.
Organizations should implement immediate mitigations including applying the latest Cisco security patches and updates that address the authorization bypass in TFTP session handling. Network segmentation should be enforced to limit access to VCS systems, particularly restricting TFTP access to authorized administrative networks only. Monitoring and logging of TFTP sessions should be enhanced to detect anomalous access patterns that may indicate exploitation attempts. Additionally, implementing role-based access controls that strictly limit MRA functionality and regularly auditing user permissions can help reduce the attack surface. This vulnerability aligns with CWE-284 (Improper Access Control) and relates to ATT&CK techniques involving privilege escalation and credential access, emphasizing the need for comprehensive security controls beyond simple patch management to protect against such sophisticated attack vectors.