Inbound IP packets with a local host loopback address (127.0.0.0/8) must be blocked, denied, or dropped at the perimeter device.

From Perimeter Router Security Technical Implementation Guide Cisco

Part of IPv4 Loopback address is not blocked

Associated with IA controls: ECSC-1

SV-15384r2_rule Inbound IP packets with a local host loopback address (127.0.0.0/8) must be blocked, denied, or dropped at the perimeter device.

Vulnerability discussion

This type of IP address spoofing occurs when someone outside the network uses a local host address to gain access to systems or devices on the internal network. If the intruder is successful, they can intercept data, passwords, etc., and use that information to perform destructive acts on or to the network.

Check content

Review the perimeter device configuration to ensure access control lists are configured to block, deny, or drop inbound IP addresses using the local host IP address space of 127.0.0.0/8. Depending on the security posture of the access control list, this requirement may be met explicitly or inexplicitly. Config Example: ! interface FastEthernet 0/0 description to NIPRNet core router ip address 199.36.92.1 255.255.255.252 ip access-group 100 in ... access-list 100 deny ip 127.0.0.0 0.255.255.255 any log !

Fix text

Configure the perimeter device to ensure access control lists are configured to block, deny, or drop inbound IP addresses using the local host IP address space of 127.0.0.0/8. Depending on the security posture of the access control list, this requirement may be met explicitly or inexplicitly.

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