RHEL 9 must ignore Internet Protocol version 4 (IPv4) Internet Control Message Protocol (ICMP) redirect messages.
An XCCDF Rule
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. This feature of the IPv4 protocol has few legitimate uses. It should be disabled unless absolutely required.
- ID
- SV-257958r991589_rule
- Version
- RHEL-09-253015
- Severity
- Medium
- References
- Updated
Remediation Templates
A Manual Procedure
Configure RHEL 9 to ignore IPv4 ICMP redirect messages.
Add or edit the following line in a single system configuration file, in the "/etc/sysctl.d/" directory:
net.ipv4.conf.all.accept_redirects = 0