Security Advisory - VRF Hopping Vulnerability in Multiple Routers

An attacker may exploit this vulnerability to forward crafted packets to MPLS links, which leads to flood attacks against the destination VPN.

The vulnerability classification has been performed by using the CVSSv2 scoring system (http://www.first.org/cvss/).

Base Score: 4.3 (AV:N/AC:M/Au:N/C:N/I:N/A:P)

Temporal Score: 3.6 (E:F/RL:O/RC:C)

Prerequisite:

1. An attacker is directly connected to the network interface for the IP address configured on the routers.
2. The attacker network and target network are at different VRF of the same routers.

Attacking procedure:

Multiple VPNs are deployed on the router in one MPLS zone. An attacker may exploit this vulnerability to forward crafted packets from one VPN to another VPN using MPLS links, which leads to flood attacks against the destination VPN.

The following are two workarounds applicable to the different boards.

Workaround 1, the following workarounds are applicable to the following boards: LPUF-10 boards used on NE40E.

Perform the following configurations by configuring the layer-2 ACL and filtering packets with labels:

In the system view, configure the layer-2 ACL by setting the Ethernet field type in the layer-2 Ethernet packet header and setting the filtering value to 0x8847 and mask to 0xFFFF. The layer-2 ACL ID ranges from 4000 to 4999. The following section uses ACL 4000 as an example.

Step 1, Configure the ACL 4000, the configuration example:

#

[NE40E]acl 4000

[NE40E-acl-ethernetframe-4000] rule permit type 8847 FFFF

Step 2, Configure the traffic classifier, the configuration example:

[NE40E]traffic classifier deny-mpls

[NE40E-classifier-deny-mpls]if-match acl 4000

Step 3, Configure the traffic behavior, the configuration example:

[NE40E]traffic behavior deny-mpls

[NE40E-behavior-deny-mpls]deny

Step 4, Configure the traffic policy, the configuration example:

[NE40E]traffic policy deny-mpls

[NE40E-trafficpolicy-deny-mpls]classifier deny-mpls behavior deny-mpls

Step 5, Apply the traffic policy to the interface, the configuration example:

[NE40E]interface GigabitEthernet 1/1/0.1

[NE40E-GigabitEthernet1/1/0.1]traffic-policy deny-mpls inbound link-layer

Workaround 2, the following workarounds are applicable to the following boards:

LPUI-41/ LPUS-41/ LPUF-100/ LPUI-100/ LPUS-100/ LPUF-50/ LPUF-51/ LPUI-51/ LPUS-51/ LPUF-101/ LPUI-101/ LPUS-101/ LPUF-102/ LPUI-102/ LPUF-120/ LPUI-120/ LPUS-120/ LPUF-240/ LPUI-240 boards used on NE40E.

Perform the following configurations by configuring MPLS ACL and filtering packets with labels:

In the system view, configure MPLS ACL by setting the filtering value to label any to filter packets with labels.

The MPLS ACL ID ranges from 10000 to 10999. The following section uses acl 10000 as an example.

Step 1, Configure the ACL 10000, the configuration example:

#

[NE40E]acl 10000

[NE40E-acl-mpls-10000]rule permit label any

Step 2, Configure the traffic classifier, the configuration example:

[NE40E]traffic classifier deny-mpls

[NE40E-classifier-deny-mpls]if-match acl 10000

Step 3, Configure the traffic behavior, the configuration example:

[NE40E]traffic behavior deny-mpls

[NE40E-behavior-deny-mpls]deny

Step 4, Configure the traffic policy, the configuration example:

[NE40E]traffic policy deny-mpls

[NE40E-trafficpolicy-deny-mpls]classifier deny-mpls behavior deny-mpls

Step 5, Apply the traffic policy to the interface, the configuration example:

[NE40E]interface GigabitEthernet 1/1/0.1

[NE40E-GigabitEthernet1/1/0.1]traffic-policy deny-mpls inbound mpls-layer

Customers should contact Huawei TAC (Huawei Technical Assistance Center) to request the upgrades. For TAC contact information, please refer to Huawei worldwide website at http://www.huawei.com/en/security/psirt/report-vulnerabilities/index.htm.

This vulnerability was reported by G. Geshev from MWR Labs. Huawei PSIRT is not aware of any public announcements or malicious use of the vulnerability described in this advisory.

For security problems about Huawei products and solutions, please contactPSIRT@huawei.com.

For general problems about Huawei products and solutions, please directly contact Huawei TAC (Huawei Technical Assistance Center) to request the configuration or technical assistance.

2015-11-10 V1.1 UPDATED added CVE ID

2015-10-21 V1.0 INITIAL

None.

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