CVE-2020-3147: Cisco Small Business Switches Denial of Service Vulnerability

A vulnerability in the web UI of Cisco Small Business Switches could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device.

The vulnerability is due to improper validation of requests sent to the web interface. An attacker could exploit this vulnerability by sending a malicious request to the web interface of an affected device. A successful exploit could allow the attacker to cause an unexpected reload of the device, resulting in a DoS condition.

Cisco has released software updates that address the vulnerability described in this advisory. There are no workarounds that address this vulnerability.

This advisory is available at the following link:

Affected Products
Vulnerable Products
This vulnerability affects the following Cisco products if they are running a firmware release earlier than

200 Series Smart Switches
300 Series Managed Switches
500 Series Stackable Managed Switches
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:

250 Series Smart Switches
350 Series Managed Switches
350X Series Stackable Managed Switches
550X Series Stackable Managed Switches
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:

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:

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 fixed this vulnerability in firmware Release for the following Cisco products:

200 Series Smart Switches
300 Series Managed Switches
500 Series Stackable Managed Switches
To download the firmware from the Software Center on, do the following:

Click Browse all.
Choose Switches > LAN Switches – Small Business.
Choose a specific product from the right pane of the product selector.
Choose Smart Switch Firmware or Switch Firmware.
Choose a release from the left pane of the page.
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.

Cisco would like to thank Ken Pyle of DFDR Consulting LLC for reporting this vulnerability.