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The system must ignore ICMPv4 redirect messages by default.


Finding ID Version Rule ID IA Controls Severity
V-38533 RHEL-06-000091 SV-50334r3_rule Low
This feature of the IPv4 protocol has few legitimate uses. It should be disabled unless it is absolutely required.
Red Hat Enterprise Linux 6 Security Technical Implementation Guide 2015-05-26


Check Text ( C-46091r2_chk )
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

The output of the command should indicate a value of "0". If this value is not the default value, investigate how it could have been adjusted at runtime, and verify it is not set improperly in "/etc/sysctl.conf".

$ grep net.ipv4.conf.default.accept_redirects /etc/sysctl.conf

If the correct value is not returned, this is a finding.
Fix Text (F-43481r1_fix)
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

If this is not the system's default value, add the following line to "/etc/sysctl.conf":

net.ipv4.conf.default.accept_redirects = 0