A vulnerability in the Precision Time Protocol (PTP) feature of Cisco Nexus 5500, 5600, and 6000 Series Switches running Cisco NX-OS Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to a lack of protection against PTP frame flood attacks. An attacker could exploit this vulnerability by sending large streams of malicious IPv4 or IPv6 PTP traffic to the affected device. A successful exploit could allow the attacker to cause a DoS condition, impacting the traffic passing through the device. 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://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20181017-nexus-ptp-dos
A vulnerability in the Precision Time Protocol (PTP) feature of Cisco Nexus 5500, 5600, and 6000 Series Switches running Cisco NX-OS Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device.
The vulnerability is due to a lack of protection against PTP frame flood attacks. An attacker could exploit this vulnerability by sending large streams of malicious IPv4 or IPv6 PTP traffic to the affected device. A successful exploit could allow the attacker to cause a DoS condition, impacting the traffic passing through the device.
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://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20181017-nexus-ptp-dos
This vulnerability affects Cisco Nexus 5500, 5600, and 6000 Series Switches that are running a vulnerable release of Cisco NX-OS Software.
For information about which Cisco NX-OS Software releases are vulnerable, see the Fixed Software section of this advisory.
Administrators can check the version of NX-OS Software running on their device by using the show version command from the device CLI. The following example identifies the 7.3(2)N1(1) release:
nx-os# 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) 2002-2017, 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 1.1.7
Power Sequencer Firmware:
Module 0: SF-Microcontroller v.0.7, SF-FPGA v.0.6
…
FPGA Firmware:
Module 0: FPGA v.0.0.0.18
…
kickstart: version 7.3(2)N1(1)
system: version 7.3(2)N1(1)
Administrators can check to see if the PTP feature is running on an affected device by issuing the following command.
The show ptp brief command displays the PTP state of all interfaces. A PTP port can be in one of the following three states or disabled:
Note: By default, PTP is disabled on the device.
The following is an example of the show ptp brief output with PTP enabled:
Vulmon
switch# sh ptp brief
PTP port status
-----------------------
Port State
------- --------------
Eth4/3 Enabled
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:
Customers who are not using the PTP feature can disable it with the no feature ptp command as shown in the following example:
To enter global configuration mode:
switch# configure terminal
Note: Enabling PTP on the switch does not enable PTP on each interface.
To enable or disable PTP on the device:
switch(config) # no feature ptp
See Cisco Nexus 5000 Series NX-OS System Management Configuration Guide for technical assistance regarding PTP.
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.
Customers are advised to upgrade to an appropriate release as indicated in the following table.
In the table, the left column lists the major releases of Cisco NX-OS Software and the second column indicates the first release that includes the fix for this vulnerability.
Nexus 5500, 5600, and 6000 Series Switches: CSCvg21830
| Cisco NX-OS Software Major Release |
First Fixed Release |
|---|---|
| Prior to 6.0 | 7.3(3)N1(1) |
| 7.0 | 7.3(3)N1(1) |
| 7.1 | 7.3(3)N1(1) |
| 7.2 | 7.3(3)N1(1) |
| 7.3 | 7.3(3)N1(1) |
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.
This vulnerability was found during the resolution of a Cisco TAC support case.
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.
| Version | Description | Section | Status | Date |
|---|---|---|---|---|
| 1.0 | Initial public release. | - | Final | 2018-October-17 |
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