Details
The telnet package contains the telnet client, which allows users to start connections to other systems via the telnet protocol.
Rationale:
The telnet protocol is insecure and unencrypted. The use of an unencrypted transmission medium could allow an unauthorized user to steal credentials. The ssh package provides an encrypted session and stronger security and is included in most Linux distributions.
Impact:
Many insecure service clients are used as troubleshooting tools and in testing environments. Uninstalling them can inhibit capability to test and troubleshoot. If they are required it is advisable to remove the clients after use to prevent accidental or intentional misuse.
Solution
Uninstall telnet:
# apt purge telnet
Supportive Information
The following resource is also helpful.
This security hardening control applies to the following category of controls within NIST 800-53: Identification and Authentication.This control applies to the following type of system Unix.