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AlmaLinux OS 9 must not send Internet Control Message Protocol (ICMP) redirects.

Overview

Finding IDVersionRule IDIA ControlsSeverity
V-269256ALMA-09-019930SV-269256r1050138_ruleCCI-000366medium
Description
ICMP redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages contain information from the system's route table possibly revealing portions of the network topology. The ability to send ICMP redirects is only appropriate for systems acting as routers.
STIGDate
Cloud Linux AlmaLinux OS 9 Security Technical Implementation Guide2026-02-27

Related Frameworks

1 mapping across 5 frameworks
SCF0 mappings

No source states a mapping between these directly.

Also reachable in 3 hops (8) derived by us, not asserted by any source

Each of these is a route we composed by chaining published mappings. No publisher states a relationship between the two endpoints.

CFG-01Configuration Management Program
1.00
END-01Endpoint Device Management (EDM)
1.00
END-04Malicious Code Protection (Anti-Malware)
1.00
END-06Endpoint File Integrity Monitoring (FIM)
1.00
MON-01Continuous Monitoring
1.00
MON-01.7File Integrity Monitoring (FIM)
1.00
CFG-02Secure Baseline Configurations
0.50
CFG-02.7Approved Configuration Deviations
0.50
NIST 800-530 mappings

No source states a mapping between these directly.

Also reachable in 2 hops (100) derived by us, not asserted by any source

Each of these is a route we composed by chaining published mappings. No publisher states a relationship between the two endpoints.

AC-12Session Termination
1.00
AC-16(1)Dynamic Attribute Association
1.00
AC-17(1)Monitoring and Control
1.00
AC-2Account Management
1.00
AC-2(1)Automated System Account Management
1.00
AC-2(11)Usage Conditions
1.00
AC-2(3)Disable Accounts
1.00
AC-2(4)Automated Audit Actions
1.00
AC-24(1)Transmit Access Authorization Information
1.00
AC-25Reference Monitor
1.00

+90 more (top 10 by confidence shown)

NIST 800-1710 mappings

No source states a mapping between these directly.

Also reachable in 3 hops (2) derived by us, not asserted by any source

Each of these is a route we composed by chaining published mappings. No publisher states a relationship between the two endpoints.

3.4.1
1.00
3.4.2
1.00
CCI1 mapping
CCI-000366
1.00
NIST CSF 2.00 mappings

No source states a mapping between these directly.

Also reachable in 3 hops (5) derived by us, not asserted by any source

Each of these is a route we composed by chaining published mappings. No publisher states a relationship between the two endpoints.

DE.CM-09
1.00
PR.PS-01
1.00
PR.DS-10
0.50
PR.PSPlatform Security
0.50
PR.PS-05
0.50

Who does this work

10 NICE work roles and 9 EC-Council certifications.

This is an inference across published mappings, not a single claim by anyone. This check maps to a control, which maps to a Cybersecurity Framework outcome, which NIST assigns to the work roles below. EC-Council separately maps its certifications to those same roles.

A certification prepares someone for a role. It is not evidence that a holder is qualified, and neither NIST nor EC-Council has stated that any certification here addresses this check.

Work-role assignments published by NIST (NICE Framework Components 2.2.0 and the CSF 2.0 OLIR crosswalk). Certification mappings published by EC-Council.

Details

Check Text (C-269256r1050138_chk)

Verify AlmaLinux OS 9 does not send ICMP redirects. Check the value of the "send_redirects" variables with the following command: $ sysctl -a | grep send_redirects net.ipv4.conf.all.send_redirects = 0 net.ipv4.conf.default.send_redirects = 0 net.ipv4.conf.enp1s0.send_redirects = 0 net.ipv4.conf.lo.send_redirects = 0 If the returned lines do not all have a value of "0", this is a finding.

Fix Text (F-73188r1049396_fix)

Configure AlmaLinux OS 9 to not allow interfaces to perform ICMP redirects. Create a numbered *.conf file in /etc/sysctl.d/ with the following content: net.ipv4.conf.all.send_redirects = 0 net.ipv4.conf.default.send_redirects = 0 net.ipv4.conf.lo.send_redirects = 0 EOF 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