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AUSCERT External Security Bulletin Redistribution
ESB-2017.2392
Cisco Small Business Managed Switches Denial of Service Vulnerability
21 September 2017
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AusCERT Security Bulletin Summary
---------------------------------
Product: Cisco Small Business 300 Series Managed Switches
Cisco Small Business 500 Series Stackable Managed Switches
Cisco 350 Series Managed Switches
Cisco 350X Series Stackable Managed Switches
Cisco 550X Series Stackable Managed Switches
Cisco ESW2 Series Advanced Switches
Publisher: Cisco Systems
Operating System: Cisco
Impact/Access: Denial of Service -- Existing Account
Resolution: Patch/Upgrade
CVE Names: CVE-2017-6720
Original Bulletin:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170920-sbms
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Cisco Security Advisory
Cisco Small Business Managed Switches Denial of Service Vulnerability
High
Advisory ID: cisco-sa-20170920-sbms
First Published: 2017 September 20 16:00 GMT
Version 1.0: Final
Workarounds: No workarounds available
Cisco Bug IDs:
CSCvb48377
CVSS Score:
Base 7.7
Base 7.7 CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H/E:X/RL:X/RC:X
CVE-2017-6720
CWE-119
Summary
A vulnerability in the Secure Shell (SSH) subsystem of Cisco Small Business
Managed Switches software could allow an authenticated, remote attacker to
cause a reload of the affected switch, resulting in a denial of service (DoS)
condition.
The vulnerability is due to improper processing of SSH connections. An
attacker could exploit this vulnerability by logging in to an affected switch
via SSH and sending a malicious SSH message.
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-20170920-sbms
Affected Products
Vulnerable Products
This vulnerability affects the following Cisco products when SSH is enabled:
Cisco Small Business 300 Series Managed Switches
Cisco Small Business 500 Series Stackable Managed Switches
Cisco 350 Series Managed Switches
Cisco 350X Series Stackable Managed Switches
Cisco 550X Series Stackable Managed Switches
Cisco ESW2 Series Advanced Switches
Notes:
SSH is not enabled on the affected platforms by default. To verify if SSH is
enabled, navigate to Security > TCP/UDP Services and look for the Enabled
checkbox next to SSH Service.
This issue is exploitable only with SSH User Authentication by Password
enabled under Security > SSH Server > SSH User Authentication. (In 2.x
software, this option is visible in Advanced display mode only.)
Products Confirmed Not Vulnerable
No other Cisco products are currently known to be affected by this
vulnerability.
Cisco has confirmed that this vulnerability does not affect the following
Cisco products:
Cisco Small Business 200 Series Smart Switches
Cisco Small Business 220 Series Smart Plus Switches
Cisco 250 Series Smart Switches
Workarounds
There are no workarounds that address this vulnerability.
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 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 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 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.
Fixed Releases
Cisco Product First Fixed Release for This
Vulnerability
Small Business 300 Series Managed
Switches
Small Business 500 Series Stackable 1.4.8.06
Managed Switches
ESW2 Series Advanced Switches
350 Series Managed Switches 2.3.0.130
350X Series Stackable Managed Switches
550X Series Stackable Managed Switches
The software can be downloaded from the Software Center on Cisco.com by
navigating to Downloads Home > Products > Switches > LAN Switches - Small
Business and selecting the respective model.
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 reported to Cisco by external researcher Alessandro
Celestra of TLogos.
URL
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170920-sbms
Revision History
Version Description Section Status Date
1.0 Initial public release. -- Final 2017-September-20
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.
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