Summary

• A vulnerability in the IOx application environment for Cisco IOS Software could allow an authenticated, remote attacker to gain unauthorized access to the Guest Operating System (Guest OS) running on an affected device.

  The vulnerability is due to incorrect role-based access control (RBAC) evaluation when a low-privileged user requests access to a Guest OS that should be restricted to administrative accounts. An attacker could exploit this vulnerability by authenticating to the Guest OS by using the low-privileged-user credentials. An exploit could allow the attacker to gain unauthorized access to the Guest OS as a root user.

  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://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190925-ios-gos-auth

  This advisory is part of the September 25, 2019, release of the Cisco IOS and IOS XE Software Security Advisory Bundled Publication, which includes 12 Cisco Security Advisories that describe 13 vulnerabilities. For a complete list of the advisories and links to them, see Cisco Event Response: September 2019 Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled Publication.

Affected Products

• Vulnerable Products

  This vulnerability affects Cisco 800 Series Industrial Integrated Services Routers and Cisco 1000 Series Connected Grid Routers (CGR 1000) that are running a vulnerable release of Cisco IOS Software with Guest OS installed.

  For information about which Cisco IOS XE Software releases are vulnerable, see the Fixed Software section of this advisory.

  Determining if Guest OS is Enabled

  Administrators can determine if Guest OS is enabled on a device by using the show iox host list detail command in the device CLI.

  The following example shows the output of the command for a device that has Guest OS enabled:

  Router#show iox host list detail | include OS status

   OS status: 		RUNNING

  If this command does not exist, or if it produces an output that does not show the string "RUNNING" within the OS Status field, the device is not affected by the vulnerability described in 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 Cisco IOS XE Software, Cisco IOS XR Software, or Cisco NX-OS Software.

Details

• The Cisco Industrial Integrated Services Routers and Cisco 1000 Series Connected Grid Routers (CGR 1000) devices are designed on a Hypervisor architecture, where IOS and a Guest OS, such as a Linux Operating system, run as two separate Virtual Machines (VMs).

  Guest OS is available as part of a bundle IOS image that contains the Hypervisor, IOS, and Guest OS images. Customers that utilized a Cisco IOS Software image bundle for performing either an initial install or for a software upgrade will have Guest OS automatically installed as part of the software image bundle installation.

  Access to the Guest OS relies on the IOS role-based access control (RBAC) and should be restricted to users who have privilege level 15 credentials on IOS. Exploitation of this vulnerability could allow the attacker to successfully log in to the Guest OS using a low-privileged IOS user credentials.

  The vulnerability described in this Advisory is localized within the Guest OS instance. Under no circumstance could an exploitation allow the attacker to gain administrative access to the IOS Software running on an affected device. For this reason, though the Common Vulnerability Scoring System (CVSS) score corresponds to a Critical qualitative representation, this vulnerability is considered HIGH Security Impact Rating (SIR).

Workarounds

• There are no workarounds that address this vulnerability.

  Disabling Guest OS eliminates the attack vector for this vulnerability and may be a suitable mitigation until affected devices can be upgraded. Administrators can uninstall Guest OS by using the guest-os image uninstall command in global configuration mode. The following example shows the output of the show platform guest-os command for a device that has Guest OS uninstalled:

  Router#show platform guest-os       
  Guest OS status:
  Installation: Unknown
  State: STOPPED

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:
  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.

  Cisco IOS Software

  To help customers determine their exposure to vulnerabilities in Cisco IOS Software, Cisco provides a tool, the Cisco IOS Software Checker, that identifies any Cisco Security Advisories that impact a specific Cisco IOS Software release and the earliest release that fixes the vulnerabilities described in each advisory (“First Fixed”). If applicable, the tool also returns the earliest release that fixes all the vulnerabilities described in all the advisories identified (“Combined First Fixed”).

  Customers can use this tool to perform the following tasks:

  • Initiate a search by choosing one or more releases from a drop-down list or uploading a file from a local system for the tool to parse
  • Enter the output of the show version command for the tool to parse
  • Create a custom search by including all previously published Cisco Security Advisories, a specific advisory, or all advisories in the most recent bundled publication

  To determine whether a release is affected by any published Cisco Security Advisory, use the Cisco IOS Software Checker on Cisco.com or enter a Cisco IOS Software release-for example, 15.1(4)M2-in the following field:

  By default, the Cisco IOS Software Checker includes results only for vulnerabilities that have a Critical or High Security Impact Rating (SIR). To include results for Medium SIR vulnerabilities, use the Cisco IOS Software Checker on Cisco.com and check the Medium check box in the Impact Rating drop-down list.

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 found during internal security testing.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190925-ios-gos-auth

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	-	Final	2019-September-25

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