Title

The system must not send ICMPv4 redirects by default. (Cat II impact)

Discussion

Sending ICMP redirects permits the system to instruct other systems to update their routing information. The ability to send ICMP redirects is only appropriate for systems acting as routers.

Check Content

The status of the "net.ipv4.conf.default.send_redirects" kernel parameter can be queried by running the following command: $ sysctl net.ipv4.conf.default.send_redirects net.ipv4.conf.default.send_redirects = 0 $ grep net.ipv4.conf.default.send_redirects /etc/sysctl.conf /etc/sysctl.d/* net.ipv4.conf.default.send_redirects = 0 If "net.ipv4.conf.default.send_redirects" is not configured in the /etc/sysctl.conf file or in the /etc/sysctl.d/ directory, is commented out, or does not have a value of "0", this is a finding.

Fix Text

To set the runtime status of the "net.ipv4.conf.default.send_redirects" kernel parameter, run the following command: # sysctl -w net.ipv4.conf.default.send_redirects=0 Set the system to the required kernel parameter by adding the following line to "/etc/sysctl.conf" or a config file in the /etc/sysctl.d/ directory (or modify the line to have the required value): net.ipv4.conf.default.send_redirects = 0 Issue the following command to make the changes take effect: # sysctl --system

Additional Identifiers

Rule ID: SV-217911r603264_rule

Vulnerability ID: V-217911

Group Title: SRG-OS-000480

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