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ALMA-09-020260 - Alma Linux OS 9 must not accept IPv4 source-routed packets by default.

Information

Source-routed packets allow the source of the packet to suggest routers forward the packet along a different path than configured on the router, which can be used to bypass network security measures. This requirement applies only to the forwarding of source-routed traffic, such as when IP forwarding is enabled and the system is functioning as a router.

Accepting source-routed packets has few legitimate uses. It must be disabled unless it is absolutely required.

Solution

Configure AlmaLinux OS 9 to ignore source-routed packets.

Create a numbered *.conf file in /etc/sysctl.d/ with the following content:

net.ipv4.conf.all.accept_source_route = 0
net.ipv4.conf.default.accept_source_route = 0
net.ipv4.conf.lo.accept_source_route = 0
net.ipv6.conf.all.accept_source_route = 0
net.ipv6.conf.default.accept_source_route = 0
net.ipv6.conf.lo.accept_source_route = 0

The system configuration files must be reloaded for the changes to take effect. To reload the contents of the files, run the following command:

$ sysctl --system

See Also

https://dl.dod.cyber.mil/wp-content/uploads/stigs/zip/U_CL_AlmaLinux_OS_9_V1R6_STIG.zip

Item Details

Category: CONFIGURATION MANAGEMENT

References: 800-53|CM-6b., CAT|II, CCI|CCI-000366, Rule-ID|SV-269259r1107619_rule, STIG-ID|ALMA-09-020260, Vuln-ID|V-269259

Plugin: Unix

Control ID: 8fa6b0b9294d965fb6443779c533176c8cc96a1f851f9dc07b6e5eb17f33ae2c