Cisco Security Advisory
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CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H/E:X/RL:X/RC:X
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A vulnerability in the Fibre Channel over Ethernet (FCoE) protocol implementation in Cisco NX-OS Software could allow an unauthenticated, adjacent attacker to cause a denial of service (DoS) condition on an affected device.
The vulnerability is due to an incorrect allocation of an internal interface index. An adjacent attacker with the ability to submit a crafted FCoE packet that crosses affected interfaces could trigger this vulnerability. A successful exploit could allow the attacker to cause a packet loop and high throughput on the affected interfaces, resulting in a DoS condition.
Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.
This advisory is available at the following link:
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190306-nexus-fbr-dos
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Vulnerable Products
This vulnerability affects the following Cisco products if they are running a vulnerable release of Cisco NX-OS Software:
- Nexus 5600 Platform Switches
- Nexus 6000 Series Switches
Note: For this vulnerability to occur, all of the following conditions must be met:
- Two vulnerable products need to be connected to each other via Ethernet ports with an incorrect internal mapping.
- The fcoe OR fcoe-npv feature must enabled.
- The vulnerable ports must not be configured for FCoE.
See the Details section for more information.
For information about which Cisco NX-OS Software releases are vulnerable, see the Fixed Software section of this advisory.
Determining the Cisco NX-OS Software Release
Administrators can check the release of Cisco NX-OS Software that is running on a device by using the show version command in the device CLI. The following example shows the output of the command for a device that is running Cisco NX-OS Software Release 7.3(4)N1(1):
nxos-switch#show version Cisco Nexus Operating System (NX-OS) Software TAC support: http://www.cisco.com/tac Documents: http://www.cisco.com/en/US/products/ps9372/tsd_products_support_series_home.html Copyright (c) 2002-2018, Cisco Systems, Inc. All rights reserved. The copyrights to certain works contained herein are owned by other third parties and are used and distributed under license. Some parts of this software are covered under the GNU Public License. A copy of the license is available at http://www.gnu.org/licenses/gpl.html. Software BIOS: version 3.6.0 Power Sequencer Firmware: Module 1: v3.0 Module 2: v5.0 Microcontroller Firmware: version v1.2.0.1 QSFP Microcontroller Firmware: Module not detected CXP Microcontroller Firmware: Module not detected kickstart: version 7.3(4)N1(1) system: version 7.3(4)N1(1) BIOS compile time: 05/09/2012 kickstart image file is: bootflash:///n5000-uk9-kickstart.7.3.4.N1.1.bin kickstart compile time: 9/10/2018 0:00:00 [09/10/2018 08:29:28] system image file is: bootflash:///n5000-uk9.7.3.4.N1.1.bin system compile time: 9/10/2018 0:00:00 [09/10/2018 12:41:33] .
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.Products Confirmed Not Vulnerable
Only products listed in the Vulnerable Products section of this advisory are known to be affected by this vulnerability.
Cisco has confirmed that this vulnerability does not affect the following Cisco products:
- Firepower 2100 Series Firewalls
- Firepower 4100 Series Next-Generation Firewalls
- Firepower 9300 Security Appliance
- MDS 9000 Series Multilayer Switches
- Nexus 1000V Switch for Microsoft Hyper-V
- Nexus 1000V Switch for VMware vSphere
- Nexus 2000 Series Fabric Extenders
- Nexus 3000 Series Switches
- Nexus 3500 Platform Switches
- Nexus 3600 Platform Switches
- Nexus 5500 Platform Switches
- Nexus 7000 Series Switches
- Nexus 7700 Series Switches
- Nexus 9000 Series Fabric Switches in Application Centric Infrastructure (ACI) mode
- Nexus 9000 Series Switches in standalone NX-OS mode
- UCS 6200 Series Fabric Interconnects
- UCS 6300 Series Fabric Interconnects
- UCS 6400 Series Fabric Interconnects
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This vulnerability requires fcoe to be enabled. To see if the fcoe or fcoe-npv feature is configured, use the show feature | include fcoe CLI command:
This vulnerability also requires that an Ethernet interface not be bound to an FCoE virtual Fibre Channel (vFC) interface. To see if an Ethernet interface is bound to a vFC interface, use the show interface brief CLI command:N5K-A# show feature | include fcoe
fcoe 1 enabled
fcoe-npv 1 disabled
In this example, Eth1/1 would not be vulnerable because it is bound to a vFC.N5K-A# show interface brief
-------------------------------------------------------------------------------
Interface Vsan Admin Admin Status SFP Oper Oper Port
Mode Trunk Mode Speed Channel
Mode (Gbps)
-------------------------------------------------------------------------------
fc1/29 200 F off notConnected swl -- 200
fc1/30 200 F off notConnected swl -- 200
fc1/31 100 F off notConnected swl -- 100
fc1/32 100 F off notConnected swl -- 100
--------------------------------------------------------------------------------
Ethernet VLAN Type Mode Status Reason Speed Port
Interface Ch #
--------------------------------------------------------------------------------
Eth1/1 1 eth trunk down SFP not inserted 10G(D) --
Eth1/2 1 eth access down SFP not inserted 10G(D) --
<snip>
--------------------------------------------------------------------------------
Port VRF Status IP Address Speed MTU
--------------------------------------------------------------------------------
mgmt0 -- up 192.168.1.2 100 1500
-------------------------------------------------------------------------------
Interface Vsan Admin Admin Status Bind Oper Oper
Mode Trunk Info Mode Speed
Mode (Gbps)
-------------------------------------------------------------------------------
vfc100 100 F on trunking 00:10:94:00:00:02 TF auto
vfc111 100 F on trunking Eth1/1 TF auto
vfc200 200 F on trunking 00:20:94:00:00:02 TF auto
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If the devices are configured as outlined in the Vulnerable Products section, a possible indicator of compromise would be a high Rx input rate on a vulnerable interface coupled with a high Tx rate for all enabled interfaces configured for the same VLAN as shown in the following example:
N6K-A# show interface eth1/2 counters brief
-------------------------------------------------------------------------------
Interface Input Rate (avg) Output Rate (avg)
------------------ ------------------
Rate Total Rate Total Rate averaging
MB/s Frames MB/s Frames interval (seconds)
-------------------------------------------------------------------------------
Eth1/2 1140 5482344 1140 5482507 30
1140 5482321 1140 5482488 300
N6K-A# show interface Ethernet 1/11 counters brief
-------------------------------------------------------------------------------
Interface Input Rate (avg) Output Rate (avg)
------------------ ------------------
Rate Total Rate Total Rate averaging
MB/s Frames MB/s Frames interval (seconds)
-------------------------------------------------------------------------------
Eth1/11 0 0 1140 5482508 30
0 0 1140 5482496 300
N6K-A# show interface Ethernet 1/16 counters brief
-------------------------------------------------------------------------------
Interface Input Rate (avg) Output Rate (avg)
------------------ ------------------
Rate Total Rate Total Rate averaging
MB/s Frames MB/s Frames interval (seconds)
-------------------------------------------------------------------------------
Eth1/16 0 0 1140 5482504 30
0 0 1140 5482565 300If there are any questions regarding the output of your device or the information above, please contact Cisco TAC:
https://www.cisco.com/c/en/us/support/web/tsd-cisco-worldwide-contacts.html
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Cisco has released free software updates that address the vulnerability described in this advisory. Customers may only install and expect support for software versions and feature sets for which they have purchased a license. By installing, downloading, accessing, or otherwise using such software upgrades, customers agree to follow the terms of the Cisco software license:
https://www.cisco.com/c/en/us/products/end-user-license-agreement.html
Additionally, customers may only download software for which they have a valid license, procured from Cisco directly, or through a Cisco authorized reseller or partner. In most cases this will be a maintenance upgrade to software that was previously purchased. Free security software updates do not entitle customers to a new software license, additional software feature sets, or major revision upgrades.
When considering software upgrades, customers are advised to regularly consult the advisories for Cisco products, which are available from the Cisco Security Advisories and Alerts page, to determine exposure and a complete upgrade solution.
In all cases, customers should ensure that the devices to be upgraded contain sufficient memory and confirm that current hardware and software configurations will continue to be supported properly by the new release. If the information is not clear, customers are advised to contact the Cisco Technical Assistance Center (TAC) or their contracted maintenance providers.Customers Without Service Contracts
Customers who purchase directly from Cisco but do not hold a Cisco service contract and customers who make purchases through third-party vendors but are unsuccessful in obtaining fixed software through their point of sale should obtain upgrades by contacting the Cisco TAC: https://www.cisco.com/c/en/us/support/web/tsd-cisco-worldwide-contacts.html
Customers should have the product serial number available and be prepared to provide the URL of this advisory as evidence of entitlement to a free upgrade.Fixed Releases
In the following table, the left column lists releases of Cisco NX-OS Software. The right column indicates whether a release is affected by the vulnerability described in this advisory and the first release that includes the fix for this vulnerability. Customers are advised to upgrade to an appropriate fixed software release as indicated in this section.
Nexus 5600 and 6000 Series Switches: CSCvn24414
Cisco NX-OS Software Release First Fixed Release for This Vulnerability Prior to 5.2 Not vulnerable 5.2 Not vulnerable 6.0 7.1(5)N1(1b) 7.0 7.1(5)N1(1b) 7.1 7.1(5)N1(1b) 7.2 7.3(5)N1(1) 7.3 7.3(5)N1(1) Additional Resources
For help determining the best Cisco NX-OS Software release for a Cisco Nexus Switch, administrators can refer to the following Recommended Releases documents. If a security advisory recommends a later release, Cisco recommends following the advisory guidance.
For help determining the best Cisco NX-OS Software release for Cisco UCS, refer to the Recommended Releases documents in the release notes for the device.Cisco MDS Series Switches
Cisco Nexus 1000V for VMware Switch
Cisco Nexus 3000 Series and 3500 Series Switches
Cisco Nexus 5000 Series Switches
Cisco Nexus 5500 Platform Switches
Cisco Nexus 6000 Series Switches
Cisco Nexus 7000 Series Switches
Cisco Nexus 9000 Series Switches
Cisco Nexus 9000 Series ACI-Mode Switches
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The Cisco Product Security Incident Response Team (PSIRT) is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.
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This vulnerability was found during the resolution of a Cisco TAC support case.
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To learn about Cisco security vulnerability disclosure policies and publications, see the Security Vulnerability Policy. This document also contains instructions for obtaining fixed software and receiving security vulnerability information from Cisco.
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Show LessVersion Description Section Status Date 1.0 Initial public release. — Final 2019-March-06
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