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The Cisco perimeter router must be configured to drop IPv6 packets containing an extension header with the Endpoint Identification option.


Overview

Finding ID Version Rule ID IA Controls Severity
V-230154 CISC-RT-000396 SV-230154r538603_rule Medium
Description
The optional and extensible natures of the IPv6 extension headers require higher scrutiny since many implementations do not always drop packets with headers that it cannot recognize, and hence could cause a Denial-of-Service on the target device. In addition, the type, length, value (TLV) formatting provides the ability for headers to be very large. This option type is associated with the Nimrod Routing system and has no defining RFC document.
STIG Date
Cisco IOS XR Router RTR Security Technical Implementation Guide 2020-09-23

Details

Check Text ( C-32468r538601_chk )
This requirement is not applicable for the DODIN Backbone.

Review the router configuration to determine if it is compliant with this requirement.

Step 1: Verify that an inbound IPv6 ACL has been configured on the external interface.

interface interface gigabitethernet 0/2/0/2
ipv6 address 2001::1:0:22/64
ipv6 access-group FILTER_IPV6 ingress

Step 2: Verify that the ACL drops IPv6 packets containing an extension header with the Endpoint Identification option as shown in the example below.

ipv6 access-list FILTER_IPV6
10 deny any any dest-option-type 138 log
20 permit ipv6 …



90 deny ipv6 any any log

If the router is not configured to drop IPv6 packets containing an extension header with the Endpoint Identification option, this is a finding.
Fix Text (F-32446r538602_fix)
Configure the router to drop IPv6 packets containing an option type values of 0x8A (Endpoint Identification) regardless of whether it appears in a Hop-by-Hop or Destination Option header as shown in the example below.

RP/0/0/CPU0:R3(config)# ipv6 access-list FILTER_IPV6
RP/0/0/CPU0:R3(config-ipv6-acl)# deny any any dest-option-type 138 log
RP/0/0/CPU0:R3(config-ipv6-acl)# permit ipv6 …



RP/0/0/CPU0:R3(config-ipv6-acl)# deny ipv6 any any log
RP/0/0/CPU0:R3(config-ipv6-acl)# exit
RP/0/0/CPU0:R3(config)# interface gigabitethernet 0/2/0/2
RP/0/0/CPU0:R3(config-if)# ipv6 access-group FILTER_IPV6 ingress
RP/0/0/CPU0:R3(config-if)# end