Title

The Juniper perimeter router must be configured to drop IPv6 packets containing the NSAP address option within Destination Option header. (Cat II impact)

Discussion

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 from RFC 1888 (OSI NSAPs and IPv6) has been deprecated by RFC 4048.

Check Content

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 IPv6 packets containing a Destination Option header with option type value of 0xC3 (NSAP address). The following example will block any inbound IPv6 packet containing a Destination Option header: Step 1: Verify that all external IPv6-enabled interfaces have an IPv6 filter as shown in the example below. interfaces { ge-0/0/0 { unit 0 { family inet6 { filter { input IPV6-INGRESS-FILTER; } address 2001:1:0:146::1/64; } } } } Step 2: Verify that the IPV6 filter blocks all packets with a Destination Option header as shown in the example below. firewall { family inet6 { filter IPV6-INGRESS-FILTER { term DEST_ OPT_HEADER { from { next-header dstops; } then { syslog; discard; } } term ALLOW_TCP_ESTABLISHED { from { next-header tcp; tcp-established; } then accept; } term DENY_BY_DEFAULT { then { syslog; discard; } } } } } Note: Currently JUNOS has no method to filter option type within Destination Option header. Hence, all packets with the Destination Option header must be dropped. If the router is not configured to drop IPv6 packets containing the NSAP address option within Destination Option header, this is a finding.

Fix Text

Step 1: Configure a filter to block packets with a Destination Option header as shown in the example. user@R1# edit firewall family inet6 user@R1# edit filter IPV6-INGRESS-FILTER user@R1# set term DEST_ OPT_HEADER from next-header dstops user@R1# set term DEST_ OPT_HEADER then discard syslog user@R1# top Step 2: Apply the filter inbound on all external IPv6-enabled interfaces. user@R1# edit interfaces ge-0/0/0 unit 0 family inet6 user@R1# set filter input IPV6-INGRESS-FILTER user@R1# commit

Additional Identifiers

Rule ID: SV-233298r604135_rule

Vulnerability ID: V-233298

Group Title: SRG-NET-000364-RTR-000205

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