STIGQter STIGQter: STIG Summary: Cisco ASA Firewall Security Technical Implementation Guide Version: 2 Release: 1 Benchmark Date: 24 Jul 2024:

The Cisco ASA must be configured to restrict it from accepting outbound packets that contain an illegitimate address in the source address field via an egress filter or by enabling Unicast Reverse Path Forwarding (uRPF).

DISA Rule

SV-239871r665899_rule

Vulnerability Number

V-239871

Group Title

SRG-NET-000364-FW-000042

Rule Version

CASA-FW-000290

Severity

CAT II

CCI(s)

Weight

10

Fix Recommendation

Configure the firewall with an egress filter or uRPF on all internal interfaces to restrict the firewall from accepting any outbound packet that contains an illegitimate address in the source field.

URF Example:

ip verify reverse-path interface INSIDE

ACL Example:

Step 1: Configure an object group containing the allowed subnets as shown in the example below.

ASA(config)# object-group network LAN_SUBNETS
ASA(config-network-object-group)# network-object 10.1.10.0 255.255.255.0
ASA(config-network-object-group)# network-object 10.1.12.0 255.255.255.0
ASA(config-network-object-group)# network-object 10.1.13.0 255.255.255.0
ASA(config-network-object-group)# network-object 10.1.22.0 255.255.255.0
ASA(config-network-object-group)# exit

Step 2: Configure the ACL.

ASA(config)# access-list INSIDE_IN permit ip object-group LAN_SUBNETS any
ASA(config)# access-list INSIDE_IN deny ip any any

Note: Traffic that is permitted must be in compliance with the PPSM.

Step 3: Apply the ACL inbound on the inside interface.

ASA(config)# access-group INSIDE_IN in interface INSIDE

Check Contents

Review the firewall configuration to verify uRPF or an egress filter has been configured on all internal interfaces to restrict the firewall from accepting outbound packets that contain an illegitimate address in the source address field.

URF Example:

ip verify reverse-path interface INSIDE

ACL Example:

Step 1: Verify that an ACL has been applied inbound on the inside interfaces as shown in the example below.

access-group INSIDE_IN in interface INSIDE

Step 2: Verify that the ACL only allows packets from legitimate internal source addresses.

object-group network LAN_SUBNETS
network-object 10.1.10.0 255.255.255.0
network-object 10.1.12.0 255.255.255.0
network-object 10.1.13.0 255.255.255.0
network-object 10.1.22.0 255.255.255.0
…
…
…
access-list INSIDE_IN extended permit ip object-group LAN_SUBNETS any
access-list INSIDE_IN extended deny ip any any

Note: Traffic that is permitted must be in compliance with the PPSM.

If uRPF or an egress ACL to restrict the firewall from accepting outbound IP packets that contain an illegitimate address in the source address field has not been configured on all internal interfaces, this is a finding.

Vulnerability Number

V-239871

Documentable

False

Rule Version

CASA-FW-000290

Severity Override Guidance

Review the firewall configuration to verify uRPF or an egress filter has been configured on all internal interfaces to restrict the firewall from accepting outbound packets that contain an illegitimate address in the source address field.

URF Example:

ip verify reverse-path interface INSIDE

ACL Example:

Step 1: Verify that an ACL has been applied inbound on the inside interfaces as shown in the example below.

access-group INSIDE_IN in interface INSIDE

Step 2: Verify that the ACL only allows packets from legitimate internal source addresses.

object-group network LAN_SUBNETS
network-object 10.1.10.0 255.255.255.0
network-object 10.1.12.0 255.255.255.0
network-object 10.1.13.0 255.255.255.0
network-object 10.1.22.0 255.255.255.0
…
…
…
access-list INSIDE_IN extended permit ip object-group LAN_SUBNETS any
access-list INSIDE_IN extended deny ip any any

Note: Traffic that is permitted must be in compliance with the PPSM.

If uRPF or an egress ACL to restrict the firewall from accepting outbound IP packets that contain an illegitimate address in the source address field has not been configured on all internal interfaces, this is a finding.

Check Content Reference

M

Target Key

5339