RHEL-09-253015 - RHEL 9 must ignore Internet Protocol version 4 (IPv4) Internet Control Message Protocol (ICMP) redirect messages.

Information

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.

Solution

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

Load settings from all system configuration files with the following command:

$ sudo sysctl --system

See Also

https://dl.dod.cyber.mil/wp-content/uploads/stigs/zip/U_RHEL_9_V2R3_STIG.zip

Item Details

Category: CONFIGURATION MANAGEMENT

References: 800-53|CM-6b., CAT|II, CCI|CCI-000366, Rule-ID|SV-257958r991589_rule, STIG-ID|RHEL-09-253015, Vuln-ID|V-257958

Plugin: Unix

Control ID: 5ce15fc05df3a0495d5ad80f748bb66c42dfe6034d1208e974287ae38ac313d2