Contec CMS8000 Patient Monitors Hidden Functionality Vulnerability Allowing Remote Code Execution

A vulnerability has been identified in the Contec CMS8000 patient monitor and its white-label OEM variants, all versions. The issue lies in the 'update' binary of the device's firmware, which hardcodes a routable IP address, bypassing the device's network settings. This functionality is triggered by pressing the 'C' button during the boot process. If an attacker can control or impersonate the specified IP address, they could exploit this vulnerability to upload and overwrite files on the device, potentially leading to unauthorized modifications or execution of malicious code.

Impact

Exploitation of this vulnerability allows for remote code execution on the affected patient monitor. This is achieved by impersonating the hardcoded IP address to upload malicious binaries that overwrite existing files on the device, including executables that are regularly executed by the monitor. Such exploitation could also be used to leak private patient information.

Reproduction

The vulnerability can be reproduced by booting the Contec CMS8000 patient monitor and pressing the 'C' button at a specific time during the boot process. This action triggers the update routine, which attempts to mount an NFS share from the hardcoded IP address 202.114.4.119. Once the connection is established, the monitor can be manipulated to download and execute malicious payloads.

Remediation

It is recommended to block all outgoing network traffic to the 202.114.4.0/24 subnet, which includes the hardcoded IP addresses used by the patient monitor. Organizations should also consider replacing these monitors with more secure alternatives, unless the vendor releases a firmware update to address the vulnerability.