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ESB-2016.0784 - [Cisco] Cisco IOS and IOS XE Software: Denial of service - Remote/unauthenticated

Date: 24 March 2016

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===========================================================================
             AUSCERT External Security Bulletin Redistribution

                               ESB-2016.0784
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
Resolution:        Patch/Upgrade
CVE Names:         CVE-2016-1349  

Original Bulletin: 
   https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20160323-smi

- --------------------------BEGIN INCLUDED TEXT--------------------

Cisco Security Advisory

Cisco IOS and IOS XE Software Smart Install Denial of Service Vulnerability

High

Advisory ID: cisco-sa-20160323-smi

Published: 2016 March 23 16:00 GMT

Version 1.0: Final

CVSS Score:

Base - 7.8

Workarounds:

No workarounds available

Cisco Bug IDs:

CSCuv45410

CVE-2016-1349

CWE-399

Summary

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:

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20160323-smi

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.

Affected Products

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.

Vulnerable Products

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.

Workarounds

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 
client feature.

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
bug CSCtj75729.

Fixed Software

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:

http://www.cisco.com/en/US/docs/general/warranty/English/EU1KEN_.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 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 
solution.

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):

http://www.cisco.com/en/US/support/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.

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
publication

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 
field:

  Check

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 
Software release.

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.

Source

This vulnerability was found and reported to Cisco by Tenable Network 
Security.

URL

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20160323-smi

Revision History

Version 	Description 		Section 	Status 		Date

1.0 		Initial public release. 		Final 		2016-March-23

Legal Disclaimer

THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF 
GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS
FOR A PARTICULAR USE. YOUR USE OF THE INFORMATION ON THE DOCUMENT OR MATERIALS
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.

- --------------------------END INCLUDED TEXT--------------------

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The University of Queensland
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