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The system must not accept IPv4 source-routed packets on any interface.


Finding ID Version Rule ID IA Controls Severity
V-217914 RHEL-06-000083 SV-217914r505923_rule Medium
Accepting source-routed packets in 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 2020-09-03


Check Text ( C-19395r376757_chk )
The status of the "net.ipv4.conf.all.accept_source_route" kernel parameter can be queried by running the following command:

$ sysctl net.ipv4.conf.all.accept_source_route
net.ipv4.conf.all.accept_source_route = 0

$ grep net.ipv4.conf.all.accept_source_route /etc/sysctl.conf /etc/sysctl.d/*
net.ipv4.conf.all.accept_source_route = 0

If "net.ipv4.conf.all.accept_source_route" 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 (F-19393r376758_fix)
To set the runtime status of the "net.ipv4.conf.all.accept_source_route" kernel parameter, run the following command:

# sysctl -w net.ipv4.conf.all.accept_source_route=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.all.accept_source_route = 0

Issue the following command to make the changes take effect:

# sysctl --system