The SUSE operating system must not allow interfaces to send Internet Protocol version 4 (IPv4) Internet Control Message Protocol (ICMP) redirect messages by default.

From SLES 12 Security Technical Implementation Guide

Associated with: CCI-000366

SV-92193r4_rule The SUSE operating system must not allow interfaces to send Internet Protocol version 4 (IPv4) Internet Control Message Protocol (ICMP) redirect messages by default.

Vulnerability discussion

ICMP redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages contain information from the system's route table, possibly revealing portions of the network topology.

Check content

Verify the SUSE operating system does not allow interfaces to perform IPv4 ICMP redirects by default. Check the value of the "default send_redirects" variables with the following command: # sysctl net.ipv4.conf.default.send_redirects net.ipv4.conf.default.send_redirects = 0 If the returned line does not have a value of "0” this is a finding.

Fix text

Configure the SUSE operating system to not allow interfaces to perform IPv4 ICMP redirects by default. Set the system to the required kernel parameter by adding the following line to "/etc/sysctl.conf" (or modify the line to have the required value): net.ipv4.conf.default.send_redirects=0 Run the following command to apply this value: # sysctl --system

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