AlmaLinux OS 9 must ignore Internet Control Message Protocol (ICMP) redirect messages.
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
| V-269244 | ALMA-09-018610 | SV-269244r1050126_rule | CCI-000366 | 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. This feature of the IP protocol has few legitimate uses. It should be disabled unless absolutely required. | ||||
| STIG | Date | |||
| Cloud Linux AlmaLinux OS 9 Security Technical Implementation Guide | 2026-02-27 | |||
Related Frameworks
4 paths across 3 frameworks
Related Frameworks
NIST 800-531 mapping
CM-6
1.00
- DISA · V1R6 · disa_xccdf · related
- DISA · 2025-01-23 · disa_cci_list · equivalent
NIST 800-1712 mappings
3.4.1
1.00
- DISA · V1R6 · disa_xccdf · related
- DISA · 2025-01-23 · disa_cci_list · equivalent
- NIST · Rev 2 (Feb 2020, errata Jan 2021) · nist_800_171_app_d · equivalent
3.4.2
1.00
- DISA · V1R6 · disa_xccdf · related
- DISA · 2025-01-23 · disa_cci_list · equivalent
- NIST · Rev 2 (Feb 2020, errata Jan 2021) · nist_800_171_app_d · equivalent
CCI1 mapping
CCI-000366
1.00
- DISA · V1R6 · disa_xccdf · related
Details
Check Text (C-269244r1050126_chk)
Verify AlmaLinux OS 9 will not accept ICMP redirect messages.
Check the value of the "accept_redirects" variables with the following command:
$ sysctl -a | grep accept_redirects
net.ipv4.conf.all.accept_redirects = 0
net.ipv4.conf.default.accept_redirects = 0
net.ipv4.conf.enp1s0.accept_redirects = 0
net.ipv4.conf.lo.accept_redirects = 0
net.ipv6.conf.all.accept_redirects = 0
net.ipv6.conf.default.accept_redirects = 0
net.ipv6.conf.enp1s0.accept_redirects = 0
net.ipv6.conf.lo.accept_redirects = 0
If the returned lines do not all have a value of "0", this is a finding.
Fix Text (F-73176r1049368_fix)
Configure AlmaLinux OS 9 to ignore ICMP redirect messages.
Create a numbered *.conf file in /etc/sysctl.d/ with the following content:
net.ipv4.conf.all.accept_redirects = 0
net.ipv4.conf.default.accept_redirects = 0
net.ipv4.conf.lo.accept_redirects = 0
net.ipv6.conf.all.accept_redirects = 0
net.ipv6.conf.default.accept_redirects = 0
net.ipv6.conf.lo.accept_redirects = 0
The system configuration files need to be reloaded for the changes to take effect. To reload the contents of the files, run the following command:
$ sysctl –system