OL 9 must ignore IPv6 Internet Control Message Protocol (ICMP) redirect messages.
Severity | Group ID | Group Title | Version | Rule ID | Date | STIG Version |
|---|---|---|---|---|---|---|
| medium | V-271878 | SRG-OS-000480-GPOS-00227 | OL09-00-006041 | SV-271878r1092346_rule | 2026-02-17 | 1 |
Description
An illicit ICMP redirect message could result in a man-in-the-middle attack.
ℹ️ Check
Note: If IPv6 is disabled on the system, this requirement is Not Applicable.
Verify that OL 9 ignores IPv6 ICMP redirect messages.
Check the value of the "accept_redirects" variables with the following command:
$ sysctl net.ipv6.conf.all.accept_redirects
net.ipv6.conf.all.accept_redirects = 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
Configure OL 9 to ignore IPv6 ICMP redirect messages.
Add or edit the following line in a single system configuration file in the "/etc/sysctl.d/" directory:
net.ipv6.conf.all.accept_redirects = 0
Load settings from all system configuration files with the following command:
$ sudo sysctl --system