ESB-2018.3501 - [Cisco] Cisco Small Business Switches: Unauthorised access - Remote/unauthenticated 2018-11-08

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             AUSCERT External Security Bulletin Redistribution

                               ESB-2018.3501
       Cisco Small Business Switches Privileged Access Vulnerability
                              8 November 2018

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        AusCERT Security Bulletin Summary
        ---------------------------------

Product:           Cisco Small Business Switches
Publisher:         Cisco Systems
Operating System:  Cisco
Impact/Access:     Unauthorised Access -- Remote/Unauthenticated
Resolution:        Patch/Upgrade
CVE Names:         CVE-2018-15439  

Original Bulletin: 
   https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20181107-sbsw-privacc

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

Cisco Small Business Switches Privileged Access Vulnerability

Priority: Critical
Advisory ID: cisco-sa-20181107-sbsw-privacc
First Published: 2018 November 7 16:00 GMT
Version 1.0: Interim
Workarounds: Yes
Cisco Bug IDs: CSCvk20713 CSCvm11846
 
CVE-2018-15439
CVSS Score:
Base 9.8
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

Summary

  * 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://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20181107-sbsw-privacc

Affected Products

  * 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

    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 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.

Details

  * 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.

Workarounds

  * 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

Fixed Software

  * 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.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 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.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 has not released software updates that address the vulnerability
    described in this advisory.

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

  * Cisco would like to thank Thor Simon of Two Sigma Investments LP for
    reporting this vulnerability.

URL

  * https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/
    cisco-sa-20181107-sbsw-privacc

Revision History

  * 
    +----------------------------------------------------------------------------+
    | Version |       Description        | Section | Status  |       Date        |
    |---------+--------------------------+---------+---------+-------------------|
    | 1.0     | Initial public release.  | -       | Interim | 2018-November-07  |
    +----------------------------------------------------------------------------+

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

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