AlmaLinux OS 9 must not accept router advertisements on all IPv6 interfaces.
Severity | Group ID | Group Title | Version | Rule ID | Date | STIG Version |
|---|---|---|---|---|---|---|
| medium | V-269243 | SRG-OS-000480-GPOS-00227 | ALMA-09-018500 | SV-269243r1050125_rule | 2025-02-20 | 1 |
| Description |
|---|
| An illicit router advertisement message could result in a man-in-the-middle attack. |
| ℹ️ Check |
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| Note: If IPv6 is disabled on the system, this requirement is Not Applicable. Verify AlmaLinux OS 9 does not accept router advertisements on any IPv6 interfaces, unless the system is a router. Determine if router advertisements are not accepted by using the following command: $ sysctl -a | grep 'accept_ra ' net.ipv6.conf.all.accept_ra = 1 net.ipv6.conf.default.accept_ra = 1 net.ipv6.conf.enp1s0.accept_ra = 0 net.ipv6.conf.lo.accept_ra = 1 If any of the returned lines are not set to "0" and it is not documented with the information system security officer (ISSO) as an operational requirement, this is a finding. |
| ✔️ Fix |
|---|
| Configure AlmaLinux OS 9 to not accept router advertisements on all IPv6 interfaces unless the system is a router. Create a numbered *.conf file in /etc/sysctl.d/ with the following content: net.ipv6.conf.all.accept_ra = 0 net.ipv6.conf.default.accept_ra = 0 net.ipv6.conf.lo.accept_ra = 0 The system configuration files need to be reloaded for the changes to take effect. To reload the contents of the files, run the following command: $ sysctl –system |