Title

The system must ignore ICMPv4 redirect messages by default. (Cat III impact)

Discussion

This feature of the IPv4 protocol has few legitimate uses. It should be disabled unless it is absolutely required.

Check Content

The status of the "net.ipv4.conf.default.accept_redirects" kernel parameter can be queried by running the following command: $ sysctl net.ipv4.conf.default.accept_redirects net.ipv4.conf.default.accept_redirects = 0 $ grep net.ipv4.conf.default.accept_redirects /etc/sysctl.conf /etc/sysctl.d/* net.ipv4.conf.default.accept_redirects = 0 If "net.ipv4.conf.default.accept_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.accept_redirects" kernel parameter, run the following command: # sysctl -w net.ipv4.conf.default.accept_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.accept_redirects = 0 Issue the following command to make the changes take effect: # sysctl --system

Additional Identifiers

Rule ID: SV-217920r603264_rule

Vulnerability ID: V-217920

Group Title: SRG-OS-000480

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