Summary

• A vulnerability in the CLI command-parsing code of the Cisco StarOS operating system for Cisco ASR 5000 Series, 5500 Series, and 5700 Series devices and Cisco Virtualized Packet Core (VPC) Software could allow an authenticated, local attacker to break from the StarOS CLI of an affected system and execute arbitrary shell commands as a Linux root user on the system.
  
  The vulnerability exists because the affected operating system does not sufficiently sanitize commands before inserting them into Linux shell commands. An attacker could exploit this vulnerability by submitting a crafted CLI command for execution in a Linux shell command as a root user. A successful exploit could allow the attacker to break from the StarOS CLI and execute arbitrary commands on the affected system as a Linux 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-20170705-asrcmd

Affected Products

• Vulnerable Products

  This vulnerability affects the following Cisco products if they are running the Cisco StarOS operating system:

  • ASR 5000 Series
  • ASR 5500 Series
  • ASR 5700 Series
  • Virtualized Packet Core-Distributed Instance (VPC-DI) Software
  • Virtualized Packet Core-Single Instance (VPC-SI) Software

  To determine whether a vulnerable release of Cisco StarOS is running on a Cisco ASR 5000 Series, 5500 Series, or 5700 Series device, administrators can issue the show version command in the device CLI. The following example shows the output of the command for a Cisco ASR 5500 Series Router that is running Cisco StarOS Release 19.2.1:

  [local]ASR-2# show version
  
  Friday August 12 13:17:31 AST 2016
  Active Software:
    Image Version:                  19.2.1
    Image Build Number:             62564
    Image Description:              Deployment_Build
    Image Date:                     Thu Dec 31 20:13:39 EST 2015
    Boot Image:                     /flash/asr5500-19.2.1.bin

  To determine whether a vulnerable release of Cisco StarOS is running on a VPC-SI or VPC-DI instance, administrators can issue the show version command in the device CLI. The following example shows the output of the command for a VPC-DI instance that is running Cisco StarOS Release 20.1.v0 (VPC-DI Release N4.6):

  [local]VPC-DI# show version
  
  Active Software:
   Image Version:                  20.1.v0
   Image Build Number:             64657
   Image Description:              Deployment_Build
   Image Date:                     Wed Jul 27 18:46:53 EDT 2016
   Boot Image:                     /flash/qvpc-di-20.1.v0.bin

  Products Confirmed Not Vulnerable

  No other Cisco products are currently known to be affected by this vulnerability.

  Cisco has confirmed that this vulnerability does not affect Cisco Elastic Services Controller (ESC) or Cisco Ultra Automation Services (UAS).

Details

• To exploit this vulnerability, the attacker could use one of several Cisco StarOS CLI commands. However, the attacker must first authenticate successfully to an affected device as a non-administrative user via the console or Secure Shell (SSH). To authenticate successfully, the attacker may use an existing, compromised, non-administrative user account for the device.

Workarounds

• There are no workarounds that address this vulnerability.

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:
  http://www.cisco.com/en/US/docs/general/warranty/English/EU1KEN_.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:
  http://www.cisco.com/en/US/support/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

  Customers should upgrade to an appropriate fixed release as indicated in the applicable table in this section.

  Cisco ASR 5000 Series, 5500 Series, and 5700 Series Devices

  In the following table, the first column lists major releases of the Cisco StarOS operating system. The second column indicates the first corresponding minor release that includes the fix for this vulnerability.

  Cisco StarOS Major Release	First Fixed Release
  18.0	18.7.6
  19.0	19.6.5
  20.0	20.2.9
  21.0	21.1.1

  Cisco Virtualized Packet Core Software

  In the following table, the first column lists major releases of Cisco Virtualized Packet Core (VPC) Software and, parenthetically, the associated release of the Cisco StarOS operating system. The second column indicates the first corresponding minor release of Cisco VPC Software that includes the fix for this vulnerability.

  Cisco VPC Software and Cisco StarOS Major Release	First Fixed Release
  N4.0 (19.2)	5.0.3 or 5.1
  N4.2 (19.3)	5.0.3 or 5.1
  N4.5 (20.0)	5.0.3 or 5.1
  N4.6 (20.1)	5.0.3 or 5.1
  N4.7 (20.2)	5.0.3 or 5.1
  N5.0 (21.0)	5.0.3

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 the resolution of a support case.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170705-asrcmd

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	-	Final	2017-July-05

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