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AUSCERT External Security Bulletin Redistribution
ESB-2018.3144
Cisco NX-OS Software for Nexus 5500, 5600, and 6000 Series Switches
Precision Time Protocol Denial of Service Vulnerability
18 October 2018
===========================================================================
AusCERT Security Bulletin Summary
---------------------------------
Product: Cisco NX-OS Software
Publisher: Cisco Systems
Operating System: Cisco
Impact/Access: Denial of Service -- Remote/Unauthenticated
Resolution: Patch/Upgrade
CVE Names: CVE-2018-0378
Original Bulletin:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20181017-nexus-ptp-dos
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Cisco NX-OS Software for Nexus 5500, 5600, and 6000 Series Switches Precision
Time Protocol Denial of Service Vulnerability
Priority: High
Advisory ID: cisco-sa-20181017-nexus-ptp-dos
First Published: 2018 October 17 16:00 GMT
Version 1.0: Final
Workarounds: No workarounds available
Cisco Bug IDs: CSCvg21830
CVE-2018-0378
CWE-20
CVSSÂ Score:
8.6 AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H/E:X/RL:X/RC:X
Summary
o 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
Affected Products
o Vulnerable Products
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.
Determining the NX-OS Software Release
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)
Determining Whether PTP is Enabled on a Device
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:
Master: The port is the source of time on the path served by the port.
Slave: The port synchronizes with the device on the path on the port
that is in the master state.
Disabled: PTP is not enabled on this port.
Passive: The port is not the master on the path, nor does it
synchronize with a master.
Note: By default, PTP is disabled on the device.
The following is an example of the show ptp brief output with PTP enabled:
switch# sh ptp brief
PTP port status
-----------------------
Port State
------- --------------
Eth1/3 Enabled
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
Firepower 4100 Series Next-Generation Firewall
Firepower 9300 Security Appliances
MDS 9000 Series Multilayer Switches
Nexus 1000V Switch for Microsoft Hyper-V
Nexus 1000V Switch for VMware vSphere
Nexus 2000 Series Switches
Nexus 3000 Series Switches
Nexus 3500 Platform Switches
Nexus 3600 Platform Switches
Nexus 4000 Series Switches
Nexus 7000 Series Switches
Nexus 9000 Series Fabric Switches in Application-Centric
Infrastructure (ACI) mode
Nexus 9000 Series Switches in standalone NX-OS mode
Nexus 9500 R-Series Line Cards and Fabric Modules
UCS 6100 Series Fabric Interconnects
UCS 6200 Series Fabric Interconnects
UCS 6300 Series Fabric Interconnects
UCS 6400 Series Fabric Interconnects
Details
o PTP is a time synchronization protocol for nodes distributed across a
network. Its hardware timestamp feature provides greater accuracy than
other time synchronization protocols such as the Network Time Protocol
(NTP). For more information on how and where to configure PTP on a device,
see Cisco Nexus 5000 Series NX-OS System Management Configuration Guide,
or contact Cisco TAC for further technical information.
Workarounds
o 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.
Fixed Software
o 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
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)
Exploitation and Public Announcements
o 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.
Source
o This vulnerability was found during the resolution of a Cisco TAC support
case.
Cisco Security Vulnerability Policy
o 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.
Subscribe to Cisco Security Notifications
o Subscribe
URL
o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20181017-nexus-ptp-dos
Revision History
o
+----------+---------------------------+----------+--------+------------------+
| Version | Description | Section | Status | Date |
+----------+---------------------------+----------+--------+------------------+
| 1.0 | Initial public release. | - | Final | 2018-October-17 |
+----------+---------------------------+----------+--------+------------------+
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