Date: 24 March 2016
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AUSCERT External Security Bulletin Redistribution
Cisco IOS and IOS XE Software Smart Install Denial of Service Vulnerability
24 March 2016
AusCERT Security Bulletin Summary
Product: Cisco IOS
Cisco IOS XE
Publisher: Cisco Systems
Operating System: Cisco
Impact/Access: Denial of Service -- Remote/Unauthenticated
CVE Names: CVE-2016-1349
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Cisco Security Advisory
Cisco IOS and IOS XE Software Smart Install Denial of Service Vulnerability
Advisory ID: cisco-sa-20160323-smi
Published: 2016 March 23 16:00 GMT
Version 1.0: Final
Base - 7.8
No workarounds available
Cisco Bug IDs:
The Smart Install client feature in Cisco IOS and IOS XE Software contains a
vulnerability that could allow an unauthenticated, remote attacker to cause a
denial of service (DoS) condition on an affected device.
The vulnerability is due to incorrect handling of image list parameters. An
attacker could exploit this vulnerability by sending crafted Smart Install
packets to TCP port 4786. A successful exploit could cause a Cisco Catalyst
switch to reload, resulting in a DoS condition.
Cisco has released software updates that address this vulnerability. There are
no workarounds that address this vulnerability other than disabling Smart
Install functionality on the vulnerable device.
This advisory is available at the following link:
This advisory is part of the March 23, 2016, release of the Cisco IOS and IOS
XE Software Security Advisory Bundled Publication, which includes six Cisco
Security Advisories that describe six vulnerabilities. All the vulnerabilities
have a Security Impact Rating of "High." For a complete list of advisories and
links to them, see Cisco Event Response: Semiannual Cisco IOS and IOS XE
Software Security Advisory Bundled Publication.
The Smart Install client feature in Cisco IOS and IOS XE Software is a
plug-and-play configuration and image-management feature that provides
zero-touch deployment for new switches. The feature allows a customer to ship
a Cisco switch to any location, install it in the network, and power it on
without additional configuration requirements.
This vulnerability affects Cisco devices that are running a vulnerable release
of Cisco IOS or IOS XE Software with the Smart Install client feature enabled.
For information about which Cisco IOS and IOS XE Software releases are
vulnerable, see the "Fixed Software" section of this advisory.
To determine whether a Cisco IOS or IOS XE device is configured with the Smart
Install client feature enabled, use the show vstack config privileged EXEC
command on the Smart Install client. The following is the output of the show
vstack config command in a Cisco Catalyst Switch configured as a Smart Install
client. The output for Role: Client from the show vstack config command
confirms that the feature is enabled on the device.
Indicators of Compromise
Exploitation of this vulnerability will cause an affected device to reload and
generate a crashinfo file. Contact the Cisco Technical Assistance Center (TAC)
to review the file and determine whether the device has been compromised by
exploitation of this vulnerability.
There are no workarounds available that address this vulnerability other than
disabling the Smart Install feature. The Smart Install Feature is enabled by
default on client switches. No configuration is needed in the client switches.
In certain releases of Cisco IOS and IOS XE Software, the Smart Install client
feature can be disabled with the global configuration command no vstack. In
certain releases of Cisco IOS and IOS XE Software where the command is
available, the vulnerability can be addressed by disabling the Smart Install
The following example shows the output of the show vstack config command in a
Cisco Catalyst Switch with the Smart Install client feature disabled:
switch#show vstack config
Role: Client (SmartInstall disabled)
Vstack Director IP address: 10.1.1.100
Note: The no vstack global configuration command to disable the Smart Install
client feature was introduced with the fix for Cisco bug CSCtj75729 (Ability
to shut Smart Install default service on TCP port 4786). If a Cisco IOS or IOS
XE Software release supports the Smart Install client feature but the no
vstack command does not exist, the release does not contain the fix for Cisco
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:
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 consult the Cisco
Security Advisories and Responses archive at http://www.cisco.com/go/psirt and
review subsequent advisories to determine exposure and a complete upgrade
In all cases, customers should ensure that the devices to upgrade 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 Technical Assistance Center (TAC):
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.
Cisco IOS and IOS XE Software
To help customers determine their exposure to vulnerabilities in Cisco IOS and
IOS XE Software, Cisco provides a tool, the Cisco IOS Software Checker, that
identifies any Cisco Security Advisories that impact a specific software
release and the earliest release that fixes the vulnerabilities described in
each advisory ("First Fixed"). If applicable, the tool also returns the
earliest release that fixes all the vulnerabilities described in all the
advisories identified ("Combined First Fixed").
Customers can use this tool to perform the following tasks:
Initiate a search by choosing one or more releases from a drop-down menu or
uploading a file from a local system for the tool to parse
Enter the output of the show version command for the tool to parse
Create a custom search by including all previously published Cisco Security
Advisories, a specific advisory, or all advisories in the most recent bundled
To determine whether a release is affected by any published Cisco Security
Advisory, use the Cisco IOS Software Checker on Cisco.com or enter a Cisco IOS
or IOS XE Software releasefor example, 15.1(4)M2 or 3.01.4Sin the following
For a mapping of Cisco IOS XE Software releases to Cisco IOS Software
releases, refer to the Cisco IOS XE 2 Release Notes, Cisco IOS XE 3S Release
Notes, or Cisco IOS XE 3SG Release Notes, depending on the Cisco IOS XE
Exploitation and Public Announcements
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 and reported to Cisco by Tenable Network
Version Description Section Status Date
1.0 Initial public release. Final 2016-March-23
THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF
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LINKED FROM THE DOCUMENT IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO
CHANGE OR UPDATE THIS DOCUMENT AT ANY TIME.
A standalone copy or paraphrase of the text of this document that omits the
distribution URL is an uncontrolled copy and may lack important information or
contain factual errors. The information in this document is intended for end
users of Cisco products.
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