Cisco Expressway Series and TelePresence Video Communication Server Image Verification Vulnerability

Vulnerability

The vulnerability resides in the image verification function of Cisco Expressway Series and Cisco TelePresence Video Communication Server (VCS). It is due to insufficient validation of the content of upgrade packages. An authenticated, remote attacker can exploit this flaw by uploading a specially crafted archive to the Upgrade page of the administrative web interface. Affected products include all versions of Cisco Expressway Series and TelePresence VCS prior to any fix.

Exploitation

An attacker must have valid administrative credentials to access the web interface. No additional user interaction is required beyond the attacker's actions. The attacker uploads a malicious upgrade package to the Upgrade page, which is then processed by the vulnerable verification function, leading to code execution.

Impact

Successful exploitation allows the attacker to execute arbitrary commands with the privileges of the _nobody account on the underlying operating system. This results in a compromise of confidentiality, integrity, and availability, albeit at a low-privilege user level.

Mitigation

Cisco has not released a software update to address this vulnerability. No workarounds exist that directly fix the flaw. However, administrative mitigations include restricting access to the management plane via firewall rules, using the Dedicated Management Interface (DMI) introduced in Release X12.7, and implementing client certificate-based authentication. These measures reduce the attack surface but do not eliminate the vulnerability. [1]