The Tenda CP3 Pro firmware contains a critical security flaw that enables the telnet service by default, creating a high risk of unauthorized remote system access.

This vulnerability involves insecure default configurations where the telnet service is initialized at boot via the /etc/init.d/eth.sh script. This flaw allows unauthenticated remote attackers to attempt connections to the device shell over the network.

The exposure of a telnet interface on network-connected hardware presents a severe risk of unauthorized administrative access. Given the CVSS score of 7.5, this vulnerability is classified as High, as it could lead to full device compromise, potential participation in botnets, or lateral movement within the internal network.

Immediate Action: Since no specific patch is currently identified, administrators should immediately disable the telnet service on all affected Tenda CP3 Pro devices if the interface allows, or isolate the devices from external network access.

Proactive Monitoring: Review device access logs for unauthorized login attempts and monitor network traffic for unexpected inbound connections on port 23.

Compensating Controls: Implement strict firewall rules to block all inbound traffic to the device on the telnet port and ensure the device is not exposed to the public internet.

Public Exploit Available: Unknown.

Due to the high severity of this vulnerability, immediate containment is required to prevent unauthorized access. Organizations should prioritize restricting network access to affected devices and monitor vendor channels for the release of a firmware update that permanently disables the vulnerable service.