Title

The system must ignore ICMPv6 redirects by default. (Cat II impact)

Discussion

An illicit ICMP redirect message could result in a man-in-the-middle attack.

Check Content

If IPv6 is disabled, this is not applicable. The status of the "net.ipv6.conf.default.accept_redirects" kernel parameter can be queried by running the following command: $ sysctl net.ipv6.conf.default.accept_redirects net.ipv6.conf.default.accept_redirects = 0 $ grep net.ipv6.conf.default.accept_redirects /etc/sysctl.conf /etc/sysctl.d/* net.ipv6.conf.default.accept_redirects = 0 If "net.ipv6.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.ipv6.conf.default.accept_redirects" kernel parameter, run the following command: # sysctl -w net.ipv6.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.ipv6.conf.default.accept_redirects = 0 Issue the following command to make the changes take effect: # sysctl --system

Additional Identifiers

Rule ID: SV-217926r603264_rule

Vulnerability ID: V-217926

Group Title: SRG-OS-000480

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