Information
ICMP Redirects are used to send routing information to other hosts. As a host itself does not act as a router (in a host only configuration), there is no need to send redirects.
Rationale:
An attacker could use a compromised host to send invalid ICMP redirects to other router devices in an attempt to corrupt routing and have users access a system set up by the attacker as opposed to a valid system.
Solution
Set the following parameters in /etc/sysctl.conf or a /etc/sysctl.d/* file:
net.ipv4.conf.all.send_redirects = 0
net.ipv4.conf.default.send_redirects = 0
Run the following commands to set the active kernel parameters:
# sysctl -w net.ipv4.conf.all.send_redirects=0
# sysctl -w net.ipv4.conf.default.send_redirects=0
# sysctl -w net.ipv4.route.flush=1
Notes:
This Benchmark recommendation maps to:
Red Hat Enterprise Linux 7 Security Technical Implementation Guide:
Version 2, Release: 3 Benchmark Date: 26 Apr 2019
Vul ID: V-72293
Rule ID: SV-86917r3_rule
STIG ID: RHEL-07-040660
Severity: CAT II
Vul ID: V-72291
Rule ID: SV-86915r4_rule
STIG ID: RHEL-07-040650
Severity: CAT II