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The Cisco perimeter router must be configured to drop IPv6 packets containing a Hop-by-Hop or Destination Option extension header with an undefined option type.
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
|---|---|---|---|---|
| V-230160 | CISC-RT-000398 | SV-230160r538618_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. |
| STIG | Date |
|---|---|
| Cisco IOS XR Router RTR Security Technical Implementation Guide | 2020-09-23 |
Details
| Check Text ( C-32472r538616_chk ) |
|---|
| This requirement is not applicable for the DODIN Backbone. Review the router configuration and determine if filters are bound to the applicable interfaces to drop all inbound IPv6 packets containing an undefined option type value regardless of whether they appear in a Hop-by-Hop or Destination Option header. Undefined values are 0x02, 0x03, 0x06, 0x9 – 0xE, 0x10 – 0x22, 0x24, 0x25, 0x27 – 0x2F, and 0x31 – 0xFF. 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 or Destination Option extension header with an undefined option type as shown in the example below. ipv6 access-list FILTER_IPV6 10 deny any any dest-option-type 2 20 deny any any dest-option-type 3 30 deny any any dest-option-type 6 40 deny any any dest-option-type 9 50 deny any any dest-option-type 10 60 deny any any dest-option-type 11 70 deny any any dest-option-type 12 80 deny any any dest-option-type 13 90 deny any any dest-option-type 14 100 deny any any dest-option-type 16 … 280 deny any any dest-option-type 34 290 deny any any dest-option-type 36 300 deny any any dest-option-type 37 310 deny any any dest-option-type 39 … 390 deny any any dest-option-type 47 400 deny any any dest-option-type 49 … nnn deny any any dest-option-type 255 nnn permit … … … … nnn deny ipv6 any any log Note: Because hop-by-hop and destination options have the same exact header format, they can be combined under the dest-option-type keyword. Since Hop-by-Hop and Destination Option headers have non-overlapping types, you can use dest-option-type to match either. If the router is not configured to drop IPv6 packets containing a Hop-by-Hop or Destination Option extension header with an undefined option type, this is a finding. |
| Fix Text (F-32450r538617_fix) |
|---|
| Configure the router to drop all inbound IPv6 packets containing an undefined option type value regardless of whether they appear 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 2 RP/0/0/CPU0:R3(config-ipv6-acl)# deny any any dest-option-type 3 RP/0/0/CPU0:R3(config-ipv6-acl)# deny any any dest-option-type 6 RP/0/0/CPU0:R3(config-ipv6-acl)# deny any any dest-option-type 9 RP/0/0/CPU0:R3(config-ipv6-acl)# deny any any dest-option-type 10 RP/0/0/CPU0:R3(config-ipv6-acl)# deny any any dest-option-type 11 RP/0/0/CPU0:R3(config-ipv6-acl)# deny any any dest-option-type 12 RP/0/0/CPU0:R3(config-ipv6-acl)# deny any any dest-option-type 13 RP/0/0/CPU0:R3(config-ipv6-acl)# deny any any dest-option-type 14 RP/0/0/CPU0:R3(config-ipv6-acl)# deny any any dest-option-type 16 … RP/0/0/CPU0:R3(config-ipv6-acl)# deny any any dest-option-type 34 RP/0/0/CPU0:R3(config-ipv6-acl)# deny any any dest-option-type 36 RP/0/0/CPU0:R3(config-ipv6-acl)# deny any any dest-option-type 37 RP/0/0/CPU0:R3(config-ipv6-acl)# deny any any dest-option-type 39 … RP/0/0/CPU0:R3(config-ipv6-acl)# deny any any dest-option-type 47 RP/0/0/CPU0:R3(config-ipv6-acl)# deny any any dest-option-type 49 … RP/0/0/CPU0:R3(config-ipv6-acl)# deny any any dest-option-type 255 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 |