The firewall must not be listening for telnet service.

From Firewall Security Technical Implementation Guide - Cisco

Part of Firewall is listening for telnet service - Cisco.

SV-87531r1_rule The firewall must not be listening for telnet service.

Vulnerability discussion

Telnet is an unencrypted service which can be easily exploited, especially when used over a public network such as the internet. With telnet enabled on the firewall, an attacker may be able to send spoofed packets through the firewall and consume the firewall’s memory, causing a denial of service on the device. Telnet service is vulnerable to many exploits which can compromise the network device if enabled.

Check content

Have the firewall admin enter the following command to verify if the firewall is listening to telnet port 23 or 1467: show asp table socket ciscoasa# show asp table socket Protocol Socket State Local Address Foreign Address TCP 0000f668 LISTEN 2.0.0.1:23 0.0.0.0:* If the firewall is listening to telnet port 23 or 1467, this is a finding.

Fix text

Disable telnet and verify the firewall is not listening to port 23 or 1467 as shown in the following example: no telnet 2.0.0.2 255.255.255.255 inside ciscoasa# show asp table socket Protocol Socket State Local Address Foreign Address ciscoasa#

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