==================================================================== CERT-Renater Note d'Information No. 2018/VULN374 _____________________________________________________________________ DATE : 08/11/2018 HARDWARE PLATFORM(S): Cisco Small Business Switches. OPERATING SYSTEM(S): Cisco Small Business Switches firmware. ===================================================================== https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20181107-sbsw-privacc _____________________________________________________________________ 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 password encrypted 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 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 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 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 | +----------------------------------------------------------------------------+ ========================================================= + CERT-RENATER | tel : 01-53-94-20-44 + + 23/25 Rue Daviel | fax : 01-53-94-20-41 + + 75013 Paris | email:cert@support.renater.fr + =========================================================