TOSS 5 must prevent Internet Protocol version 6 (IPv6) Internet Control Message Protocol (ICMP) redirect messages from being accepted.
Severity | Group ID | Group Title | Version | Rule ID | Date | STIG Version |
|---|---|---|---|---|---|---|
| medium | V-282703 | SRG-OS-000480-GPOS-00227 | TOSS-05-000231 | SV-282703r1201358_rule | 2026-04-01 | 1 |
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.
ℹ️ Check
Verify TOSS 5 will not accept IPv6 ICMP redirect messages.
Note: If IPv6 is disabled on the system, this requirement is not applicable.
Check the value of the default "accept_redirects" variables using the following command:
$ sudo sysctl net.ipv6.conf.default.accept_redirects
net.ipv6.conf.default.accept_redirects = 0
If the returned line does not have a value of "0", or a line is not returned, this is a finding.
✔️ Fix
Configure TOSS 5 to prevent IPv6 ICMP redirect messages from being accepted.
Add or edit the following line in a single system configuration file, in the "/etc/sysctl.d/" directory:
net.ipv6.conf.default.accept_redirects = 0
Load settings from all system configuration files using the following command:
$ sudo sysctl --system