Cayin CMS suffers from an authenticated OS semi-blind command injection vulnerability using default credentials. This can be exploited to inject and execute arbitrary shell commands as the root user through the 'NTP_Server_IP' HTTP POST parameter in system.cgi page. This issue affects several branches and versions of the CMS application, including CME-SE, CMS-60, CMS-40, CMS-20, and CMS version 8.2, 8.0, and 7.5.