Executive Summary

CVE-2020-36910 is an authenticated remote command injection vulnerability in Cayin Signage Media Player 3.0 and related versions. It occurs due to improper sanitization of the 'NTP_Server_IP' parameter in the system.cgi and wizard_system.cgi web interface pages. An attacker who has authenticated access using default credentials can inject arbitrary shell commands through this parameter, which are then executed with root privileges on the device. This allows the attacker to fully compromise the system. [1, 2, 4, 5]

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Impact Analysis

This vulnerability allows an attacker with authenticated access and default credentials to execute arbitrary commands as the root user on affected Cayin Signage Media Player devices. This can lead to full system compromise, including unauthorized access to sensitive data, starting or stopping services, denial of service (DoS), and complete control over the device. [1, 2, 4, 5]

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Detection Guidance

This vulnerability can be detected by attempting to exploit the 'NTP_Server_IP' parameter on the system.cgi or wizard_system.cgi web interface pages using default credentials (username: 'webadmin', password: 'admin'). Commands such as `id` (to check user privileges), `netstat` (to check open ports), or reading sensitive files like `/etc/passwd` have been demonstrated to confirm exploitation. Detection involves sending crafted HTTP GET requests with injected shell commands in the 'NTP_Server_IP' parameter and observing the response for command output. A proof-of-concept Python script (cayin_smp.py) is available that automates this detection by authenticating with default credentials and injecting commands to verify vulnerability. [4, 5]

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Mitigation Strategies

Immediate mitigation steps include changing the default credentials (username: 'webadmin', password: 'admin') to strong, unique passwords to prevent unauthorized authenticated access. Additionally, restrict network access to the web management interface to trusted users only. If possible, disable or restrict access to the vulnerable system.cgi and wizard_system.cgi pages or apply any available patches or updates from the vendor. Monitoring and blocking suspicious requests targeting the 'NTP_Server_IP' parameter can also help reduce risk until a patch is applied. [1, 2, 4]

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