Cisco Security Advisory
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CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:X/RL:X/RC:X
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A vulnerability in the Cisco Small Business Switches software could allow an unauthenticated, remote attacker to bypass the user authentication mechanism of an affected device.
The vulnerability exists because under specific circumstances, the affected software enables a privileged user account without notifying administrators of the system. An attacker could exploit this vulnerability by using this account to log in to an affected device and execute commands with full admin rights.
Cisco has not released software updates that address this vulnerability. This advisory will be updated with fixed software information once fixed software becomes available. There is a workaround to address this vulnerability.
This advisory is available at the following link:
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20181107-sbsw-privacc
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Vulnerable Products
This vulnerability affects the following Cisco Small Business product families running any software release if no user accounts with access privilege set to level 15 are configured on the device:
- Cisco Small Business 200 Series Smart Switches
- Cisco Small Business 300 Series Managed Switches
- Cisco Small Business 500 Series Stackable Managed Switches
- Cisco 250 Series Smart Switches
- Cisco 350 Series Managed Switches
- Cisco 350X Series Stackable Managed Switches
- Cisco 550X Series Stackable Managed Switches
Determining the Cisco Small Business Switches Software Release
To determine which Cisco Small Business Switches Software release is running on a device, use the show version command from the CLI prompt. The following example shows the output of the command for a device that is running software version 1.4.9.4:
Switch# show version SW version 1.4.9.04 (date 20-Jul-2018 time 17:14:12)
Determining If Privilege Level 15 User Accounts Are Present on the Device Configuration
To determine if any privilege level 15 user accounts are present in the device configuration, use the command show running-config | include privilege 15 from a CLI prompt. An empty output would indicate that no user accounts with level 15 access privilege are configured on the device; the device is vulnerable if also running an affected software release.
The following example shows the output of the command show running-config | include privilege 15 when a user account with access privilege set to level 15 is not present on the running configuration.
Switch# show running-config | include privilege 15 Switch#
The following example shows the output of the command show running-config | include privilege 15 when a user account with access privilege set to level 15 is present on the running configuration. This device is not vulnerable:
Switch# show running-config | include privilege 15 username <user-ID> password encrypted <encrypted-password> privilege 15
Note: Some hardware/software combinations may not support the piping (“|”) of commands. In that case, use the command show running-config with no pipes and scan the output for the relevant configuration lines.
Additional information is available in the Details section of this advisory.
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:
- Cisco 200E Series Smart Switches
- Cisco 220 Series Smart Switches
Cisco has also confirmed that this vulnerability does not affect devices running Cisco IOS Software, Cisco IOS XE Software, or Cisco NX-OS Software.
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Cisco Small Business Switches are typically deployed within small office/home office (SOHO) network environments. The default configuration on the devices listed as vulnerable includes a default, privileged user account that is used for the initial login and cannot be removed from the system. An administrator may disable this account by configuring other user accounts with access privilege set to level 15. However, if all user-configured privilege level 15 accounts are removed from the device configuration, an affected software release re-enables the default privileged user account without notifying administrators of the system. Under these circumstances, an attacker can use this account to log in to an affected device and execute commands with full admin rights.
Note: The default user account is defined in a software-internal data structure and is not visible in either the running configuration or the startup configuration of an affected device.
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The workaround consists of adding at least one user account with access privilege set to level 15 in the device configuration. The following example shows how to configure an account by using admin as user ID, setting the access privilege to level 15, and defining the password by replacing <strong_password> with a complex password chosen by the user. By adding this user account, the default privileged account will be disabled.
Switch# configure terminal Switch(config)# username admin privilege 15 password <strong_password>
The command show running-config | include privilege 15 will now produce the following output:
Switch# show running-config | include privilege 15 username admin password encrypted <encrypted-password> privilege 15
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Cisco has not released software updates that address this vulnerability.
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.htmlAdditionally, 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.htmlCustomers 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 has not released software updates that address the vulnerability described in this advisory.
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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.
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Cisco would like to thank Thor Simon of Two Sigma Investments LP for reporting this vulnerability.
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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.
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Show LessVersion Description Section Status Date 1.2 Updated the Products Confirmed Not Vulnerable section Vulnerable Products Interim 2019-January-16 1.1 Added note about pipes to "Determining If Privilege Level 15 User Accounts Are Present on the Device Configuration" Vulnerable Products Interim 2018-November-12 1.0 Initial public release. — Interim 2018-November-07
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