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The Cisco perimeter switch must be configured to drop IPv6 packets containing a Hop-by-Hop header with invalid option type values.


Overview

Finding ID Version Rule ID IA Controls Severity
V-237766 CISC-RT-000394 SV-237766r856667_rule Medium
Description
These options are intended to be for the Destination Options header only. 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.
STIG Date
Cisco IOS-XE Switch RTR Security Technical Implementation Guide 2022-09-13

Details

Check Text ( C-40978r856259_chk )
This requirement is not applicable for the DODIN Backbone.

Review the switch 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 gigabitethernet1/0
ipv6 address 2001::1:0:22/64
ipv6 traffic-filter FILTER_IPV6 in


Step 2: Verify that the ACL drops IPv6 packets containing a Hop-by-Hop header with option type values of 0x04 (Tunnel Encapsulation Limit), 0xC9 (Home Address Destination), or 0xC3 (NSAP Address) as shown in the example below.

ipv6 access-list FILTER_IPV6
deny hbh any any dest-option-type 4 log
deny hbh any any dest-option-type 195 log
deny hbh any any dest-option-type home-address log
permit ipv6 …



deny ipv6 any any log


If the switch is not configured to drop IPv6 packets containing a Hop-by-Hop header with invalid option type values, this is a finding.
Fix Text (F-40940r856260_fix)
Configure the switch to drop IPv6 packets containing a Hop-by-Hop header with invalid option type values as shown in the example below.

SW1(config)#ipv6 access-list FILTER_IPV6
SW1(config-ipv6-acl)#deny hbh any any dest-option-type 4 log
SW1(config-ipv6-acl)#deny hbh any any dest-option-type 195 log
SW1(config-ipv6-acl)#deny hbh any any dest-option-type home-address log
SW1(config-ipv6-acl)# permit ipv6 …



SW1(config-ipv6-acl)#deny ipv6 any any log
SW1(config-ipv6-acl)#exit
SW1(config)#int g1/0
SW1(config-if)#ipv6 traffic-filter FILTER_IPV6
SW1(config-if)#end