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The Oracle Linux operating system must prevent Internet Protocol version 4 (IPv4) Internet Control Message Protocol (ICMP) redirect messages from being accepted.
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
|---|---|---|---|---|
| V-221878 | OL07-00-040640 | SV-221878r505922_rule | Medium |
| Description |
|---|
| ICMP redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages modify the host's route table and are unauthenticated. An illicit ICMP redirect message could result in a man-in-the-middle attack. |
| STIG | Date |
|---|---|
| Oracle Linux 7 Security Technical Implementation Guide | 2020-09-10 |
Details
| Check Text ( C-23593r419706_chk ) |
|---|
| Verify the system will not accept IPv4 ICMP redirect messages. # grep 'net.ipv4.conf.default.accept_redirects' /etc/sysctl.conf /etc/sysctl.d/* If "net.ipv4.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. Check that the operating system implements the value of the "accept_redirects" variables with the following command: # /sbin/sysctl -a | grep 'net.ipv4.conf.default.accept_redirects' net.ipv4.conf.default.accept_redirects = 0 If the returned line does not have a value of "0", this is a finding. |
| Fix Text (F-23582r419707_fix) |
|---|
| Set the system to not accept IPv4 ICMP redirect messages by adding the following line to "/etc/sysctl.conf" or a configuration file in the /etc/sysctl.d/ directory (or modify the line to have the required value): net.ipv4.conf.default.accept_redirects = 0 Issue the following command to make the changes take effect: # sysctl --system |