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V-253130

CAT II (Medium)

TOSS must prevent IPv4 Internet Control Message Protocol (ICMP) redirect messages from being accepted.

Rule ID

SV-253130r991589_rule

STIG

Tri-Lab Operating System Stack (TOSS) 4 Security Technical Implementation Guide

Version

V2R5

CCIs

CCI-000366

Discussion

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.

Check Content

Verify TOSS will not accept IPv4 ICMP redirect messages.

Note: If IPv4 is disabled on the system, this requirement is Not Applicable.

Check the value of the default "accept_redirects" variables with the following command:

$ sudo sysctl net.ipv4.conf.default.accept_redirects

net.ipv4.conf.default.accept_redirects = 0

If the returned line does not have a value of "0", a line is not returned, or the line is commented out, this is a finding.

Fix Text

Configure TOSS to prevent IPv4 ICMP redirect messages from being accepted with the following command:

$ sudo sysctl -w net.ipv4.conf.default.accept_redirects=0

If "0" is not the system's default value then add or update the following line in the appropriate file under "/etc/sysctl.d":

net.ipv4.conf.default.accept_redirects=0