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The Ubuntu operating system must prevent Internet Protocol version 4 (IPv4) Internet Control Message Protocol (ICMP) redirect messages from being accepted.
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
|---|---|---|---|---|
| V-215149 | UBTU-16-030560 | SV-215149r508033_rule | Medium |
| Description |
|---|
| Internet Control Message Protocol (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 |
|---|---|
| Canonical Ubuntu 16.04 LTS Security Technical Implementation Guide | 2020-09-03 |
Details
| Check Text ( C-16348r285315_chk ) |
|---|
| Verify the Ubuntu operating system will not accept IPv4 Internet Control Message Protocol (ICMP) redirect messages. 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", or a line is not returned, this is a finding. |
| Fix Text (F-16346r285316_fix) |
|---|
| Configure the Ubuntu operating system to prevent Internet Protocol version 4 (IPv4) Internet Control Message Protocol (ICMP) redirect messages from being acceptedr 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 "/etc/sysctl.conf" or in the appropriate file under "/etc/sysctl.d": net.ipv4.conf.default.accept_redirects=0 |