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RHEL 9 must not accept router advertisements on all IPv6 interfaces by default.
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
|---|---|---|---|---|
| V-257975 | RHEL-09-254030 | SV-257975r991589_rule | Medium |
| Description |
|---|
| An illicit router advertisement message could result in a man-in-the-middle attack. |
| STIG | Date |
|---|---|
| Red Hat Enterprise Linux 9 Security Technical Implementation Guide | 2024-06-04 |
Details
| Check Text ( C-61716r943006_chk ) |
|---|
| Verify RHEL 9 does not accept router advertisements on all IPv6 interfaces by default, unless the system is a router. Note: If IPv6 is disabled on the system, this requirement is Not Applicable. Determine if router advertisements are not accepted by default by using the following command: $ sudo sysctl net.ipv6.conf.default.accept_ra net.ipv6.conf.default.accept_ra = 0 If the "accept_ra" value is not "0" and is not documented with the information system security officer (ISSO) as an operational requirement, this is a finding. Check that the configuration files are present to enable this network parameter. $ sudo /usr/lib/systemd/systemd-sysctl --cat-config | egrep -v '^(#|;)' | grep -F net.ipv6.conf.default.accept_ra | tail -1 net.ipv6.conf.default.accept_ra = 0 If "net.ipv6.conf.default.accept_ra" is not set to "0" or is missing, this is a finding. |
| Fix Text (F-61640r925911_fix) |
|---|
| Configure RHEL 9 to not accept router advertisements on all IPv6 interfaces by default unless the system is a router. Add or edit the following line in a single system configuration file, in the "/etc/sysctl.d/" directory: net.ipv6.conf.default.accept_ra = 0 Load settings from all system configuration files with the following command: $ sudo sysctl --system |