Summary

• Multiple vulnerabilities in the Cisco IOx application environment of Cisco 809 and 829 Industrial Integrated Services Routers (Industrial ISRs) and Cisco 1000 Series Connected Grid Routers (CGR1000) that are running Cisco IOS Software could allow an attacker to cause a denial of service (DoS) condition or execute arbitrary code with elevated privileges on an affected device.

  For more information about these vulnerabilities, see the Details section of this advisory.

  Cisco has released software updates that address these vulnerabilities. There are no workarounds that address these vulnerabilities.

  This advisory is available at the following link:
  https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ios-iot-gos-vuln-s9qS8kYL

  This advisory is part of the June 3, 2020, release of the Cisco IOS and IOS XE Software Security Advisory Bundled Publication, which includes 23 Cisco Security Advisories that describe 25 vulnerabilities. For a complete list of the advisories and links to them, see Cisco Event Response: June 2020 Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled Publication.

Affected Products

• Vulnerable Products

  These vulnerabilities affect the following Cisco products if they are running a vulnerable release of Cisco IOS Software:

  • Cisco 809 and 829 Industrial ISRs
  • CGR1000

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

  Note: Cisco Industrial ISRs and Cisco CGR1000 devices are designed on a hypervisor architecture, where Cisco IOS Software and a Guest OS, such as a Linux operating system, run as two separate virtual machines (VMs). Cisco IOS Software and Guest OS perform inter-VM signaling and control operations by establishing a TCP-based channel.

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

  Products Confirmed Not Vulnerable

  Only products listed in the Vulnerable Products section of this advisory are known to be affected by these vulnerabilities.

  Cisco has confirmed that these vulnerabilities do not affect the following Cisco products:

  • 800 Series ISRs
  • 807 Industrial ISRs
  • IOS XE Software
  • IOS XR Software
  • NX-OS Software

Details

• Two vulnerabilities in the Cisco IOx application environment of Cisco 809 and 829 Industrial ISRs and Cisco CGR1000 devices that are running Cisco IOS Software could allow an attacker to cause a DoS condition or execute arbitrary code with elevated privileges on an affected device.

  These vulnerabilities reside in either the ingress packet processing functionality or the implementation of the inter-VM communication channel of Cisco IOS Software for the affected products.

  The vulnerabilities are not dependent on one another; exploitation of one of the vulnerabilities is not required to exploit the other vulnerability.

  Vulnerability Details

  Details about the vulnerabilities are as follows.

  Cisco IOx Application Environment for IOS Software for Cisco Industrial Routers Remote Code Execution Vulnerability

  A vulnerability in the implementation of the inter-VM communication channel of Cisco IOS Software for Cisco 800 Series Industrial ISRs and Cisco CGR1000 devices could allow an authenticated, local attacker to execute arbitrary code on an affected system with high privileges.

  The vulnerability is due to incorrect bounds checking of certain type, length, value (TLV) fields of signaling packets that are exchanged between Cisco IOS Software and Guest OS. An attacker could exploit this vulnerability by authenticating to the device by using low-privileged-user credentials and then sending crafted signaling packets while establishing a TCP session destined to the process that manages the inter-VM communication of an affected device. When the packets are processed, an exploitable buffer overflow condition may occur. A successful exploit could allow the attacker to execute arbitrary code in the context of the Cisco IOS Software VM running on an affected device.

  This vulnerability can be exploited by using malicious TCP packets over either IPv4 or IPv6.

  Bug ID(s): CSCvr15042
  CVE ID: CVE-2020-3257
  Security Impact Rating (SIR): High
  CVSS Base Score: 7.8
  CVSS Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

  Mitigation for CVE-2020-3257

  Customers who do not use Guest OS can disable the virtual interface that is managed by Cisco IOS Software. This interface provides connectivity between the Cisco IOS Software VM and Guest OS. Configuring the virtual interface in shutdown mode eliminates the attack vector for this vulnerability and may be a suitable mitigation until affected devices can be upgraded. Applying this mitigation will prevent further access to Guest OS.

  The following table identifies the virtual interface for each affected Cisco product:

  Cisco Product	Virtual Interface
  809 Industrial ISRs	Gigabit Ethernet 2
  829 Industrial ISRs	Gigabit Ethernet 5
  CGR1000	Gigabit Ethernet 0/1

  Administrators can configure the interface in shutdown mode by entering the shutdown command in interface configuration mode. The following example shows the output of the show run interface gigabitEthernet <id> command for a device that has an interface in shutdown mode:

  Router#show run interface gigabitEthernet  | i shutdown
    Shutdown

  Cisco IOx Application Environment for IOS Software for Cisco Industrial Routers Guest OS Denial of Service Vulnerability

  A vulnerability in the ingress packet processing functionality of Cisco IOS Software for Cisco 809 and 829 Industrial ISRs and Cisco CGR1000 devices could allow an unauthenticated, adjacent attacker to shut down, reload, or uninstall the Guest OS instance running on an affected device, resulting in a DoS condition.

  The vulnerability is due to insufficient isolation of an internal, emulated Ethernet interface that should not process traffic from outside the device when the traffic is destined for the 127.0.0.0/8 range. An attacker could exploit this vulnerability by sending malicious IP packets. A successful exploit could allow the attacker to shut down, reload, or uninstall the Guest OS instance running on an affected device.

  Bug ID(s): CSCvq68872
  CVE ID: CVE-2020-3199
  Security Impact Rating (SIR): High
  CVSS Base Score: 8.1
  CVSS Vector: CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

  Determine Whether Guest OS Is Enabled

  Administrators can determine whether Guest OS is enabled on a device by using the show iox host list detail | include OS status 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 output that does not show the string RUNNING in the OS status field, the device is not affected by this vulnerability.

Workarounds

• There are no workarounds that address these vulnerabilities.

Fixed Software

• Cisco has released free software updates that address the vulnerabilities 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 the Cisco Software Checker to identify 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 the Cisco Software Checker to search advisories in the following ways:

  • Choose the software and one or more releases
  • Upload a .txt file that includes a list of specific releases
  • Enter the output of the show version command

  After initiating a search, customers can customize the search to include all Cisco Security Advisories, a specific advisory, or all advisories in the most recent bundled publication.

  Customers can use the following form to determine whether a release is affected by any Cisco Security Advisory by entering a Cisco IOS Software release-for example, 15.1(4)M2:

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

Exploitation and Public Announcements

• The Cisco Product Security Incident Response Team (PSIRT) is not aware of any public announcements or malicious use of the vulnerabilities that are described in this advisory.

Source

• These vulnerabilities were found during internal security testing by X.B. of the Cisco Advanced Security Initiatives Group (ASIG) and E.I. of Cisco PSIRT.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ios-iot-gos-vuln-s9qS8kYL

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	-	Final	2020-JUN-03

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