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The Cisco perimeter router 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-230147 | CISC-RT-000394 | SV-230147r538509_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 XR Router RTR Security Technical Implementation Guide | 2020-09-23 |
Details
| Check Text ( C-32463r538507_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 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 10 deny hbh any any dest-option-type 4 log 20 deny hbh any any dest-option-type 195 log 30 deny hbh any any dest-option-type home-address log 40 permit ipv6 … … … … 90 deny ipv6 any any log If the router 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-32441r538508_fix) |
|---|
| Drop IPv6 packets containing a Hop-by-Hop 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 hbh any any dest-option-type 4 log RP/0/0/CPU0:R3(config-ipv6-acl)# deny hbh any any dest-option-type 195 log RP/0/0/CPU0:R3(config-ipv6-acl)# deny hbh any any dest-option-type home-address 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 |