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The Photon operating system must prevent IPv4 Internet Control Message Protocol (ICMP) redirect messages from being accepted.


Overview

Finding ID Version Rule ID IA Controls Severity
V-239177 PHTN-67-000106 SV-239177r816660_rule Medium
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.
STIG Date
VMware vSphere 6.7 Photon OS Security Technical Implementation Guide 2022-06-17

Details

Check Text ( C-42388r675337_chk )
At the command line, execute the following command:

# /sbin/sysctl -a --pattern "net.ipv4.conf.(all|default|eth.*).accept_redirects"

Expected result:

net.ipv4.conf.all.accept_redirects = 0
net.ipv4.conf.default.accept_redirects = 0
net.ipv4.conf.eth0.accept_redirects = 0

If the output does not match the expected result, this is a finding.

Note: The number of "ethx" lines returned is dependent on the number of interfaces. Every "ethx" entry must be set to "0".
Fix Text (F-42347r816659_fix)
Open /etc/sysctl.conf with a text editor.

Add or update the following lines:

net.ipv4.conf.all.accept_redirects = 0
net.ipv4.conf.default.accept_redirects = 0
net.ipv4.conf.eth0.accept_redirects = 0

Run the following command to load the new setting:

# /sbin/sysctl --load