OL 8 must use reverse path filtering on all IPv4 interfaces.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-248893	SRG-OS-000480-GPOS-00227	OL08-00-040285	SV-248893r1156652_rule	2025-12-08	2

Description
It is detrimental for operating systems to provide, or install by default, functionality exceeding requirements or mission objectives. These unnecessary capabilities or services are often overlooked and therefore may remain unsecured. They increase the risk to the platform by providing additional attack vectors. Enabling reverse path filtering drops packets with source addresses that are not routable. There is no equivalent filter for IPv6 traffic. The sysctl --system command will load settings from all system configuration files. All configuration files are sorted by their filename in lexicographical order, regardless of the directories in which they reside. If multiple files specify the same option, the entry in the file with the lexicographically latest name will take precedence. Files are read from directories in the following list from top to bottom. Once a file of a given filename is loaded, any file of the same name in subsequent directories is ignored. /etc/sysctl.d/.conf /run/sysctl.d/.conf /usr/local/lib/sysctl.d/.conf /usr/lib/sysctl.d/.conf /lib/sysctl.d/*.conf /etc/sysctl.conf

Description

It is detrimental for operating systems to provide, or install by default, functionality exceeding requirements or mission objectives. These unnecessary capabilities or services are often overlooked and therefore may remain unsecured. They increase the risk to the platform by providing additional attack vectors. Enabling reverse path filtering drops packets with source addresses that are not routable. There is no equivalent filter for IPv6 traffic. The sysctl --system command will load settings from all system configuration files. All configuration files are sorted by their filename in lexicographical order, regardless of the directories in which they reside. If multiple files specify the same option, the entry in the file with the lexicographically latest name will take precedence. Files are read from directories in the following list from top to bottom. Once a file of a given filename is loaded, any file of the same name in subsequent directories is ignored. /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /lib/sysctl.d/*.conf /etc/sysctl.conf

ℹ️ Check
Verify OL 8 uses reverse path filtering on all IPv4 interfaces with the following commands: $ sysctl net.ipv4.conf.all.rp_filter net.ipv4.conf.all.rp_filter = 1 If the returned line does not have a value of "1", or a line is not returned, this is a finding.

✔️ Fix
Configure OL 8 to use reverse path filtering on all IPv4 interfaces. Add or edit the following line in a single system configuration file in the "/etc/sysctl.d/" directory: net.ipv4.conf.all.rp_filter = 1 The system configuration files must be reloaded for the changes to take effect. To reload the contents of the files, run the following command: $ sudo sysctl --system