RHEL 8 must not forward IPv4 source-routed packets by default.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-244552	RHEL-08-040249	SV-244552r743905_rule		Medium

Description
Source-routed packets allow the source of the packet to suggest that routers forward the packet along a different path than configured on the router, which can be used to bypass network security measures. This requirement applies only to the forwarding of source-routed traffic, such as when forwarding is enabled and the system is functioning as a router.

STIG	Date
Red Hat Enterprise Linux 8 Security Technical Implementation Guide	2021-06-14

Details

Check Text ( C-47827r743903_chk )

Verify RHEL 8 does not accept IPv4 source-routed packets by default. Note: If IPv4 is disabled on the system, this requirement is Not Applicable. Check the value of the accept source route variable with the following command: $ sudo sysctl net.ipv4.conf.default.accept_source_route net.ipv4.conf.default.accept_source_route = 0 If the returned line does not have a value of "0", a line is not returned, or the line is commented out, this is a finding.

Fix Text (F-47784r743904_fix)
Configure RHEL 8 to not forward IPv4 source-routed packets by default with the following command: $ sudo sysctl -w net.ipv4.conf.default.accept_source_route=0 If "0" is not the system's default value then add or update the following line in the appropriate file under "/etc/sysctl.d": net.ipv4.conf.default.accept_source_route=0