Summary

• A vulnerability in the reassembly logic for fragmented IPv4 packets of Cisco StarOS running on virtual platforms could allow an unauthenticated, remote attacker to trigger a reload of the npusim process, resulting in a denial of service (DoS) condition. There are four instances of the npusim process running per Service Function (SF) instance, each handling a subset of all traffic flowing across the device. It is possible to trigger a reload of all four instances of the npusim process around the same time.

  The vulnerability is due to improper handling of fragmented IPv4 packets containing options. An attacker could exploit this vulnerability by sending a malicious IPv4 packet across an affected device. An exploit could allow the attacker to trigger a restart of the npusim process, which will result in all traffic queued toward this instance of the npusim process to be dropped while the process is restarting. The npusim process typically restarts within less than a second.

  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://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180711-staros-dos

Affected Products

• Vulnerable Products

  This vulnerability affects the following Cisco products running any release of the StarOS operating system prior to the first fixed release:

  • Cisco Virtualized Packet Core-Single Instance (VPC-SI)
  • Cisco Virtualized Packet Core-Distributed Instance (VPC-DI)
  • Cisco Ultra Packet Core (UPC)

  To determine whether a vulnerable release of Cisco StarOS is running on an affected instance, administrators can use 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 19.3.v5 (VPC−DI Release N4.2.5):

  [local]VPC-001# show version
  
  Active Software:
    Image Version:                  19.3.v5
    Image Build Number:             65002
    Image Description:              Deployment_Build
    Image Date:                     Wed Sep 14 05:35:14 EDT 2016
    Boot Image:                     /flash/qvpc-di-19.3.v5.bin

  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 the following products are not affected by this vulnerability:

  • Cisco ASR 5000 Series Aggregation Services Routers
  • Cisco Elastic Services Controllers (ESC)
  • Cisco Ultra Automation Services (UAS)

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:
  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

  Customers should upgrade to an appropriate release as indicated in the following table:

  Cisco StarOS Release	First Fixed Release for This Vulnerability
  N5.0 (21.0)	Migrate to N5.1.11 (21.6.5)
  N5.1 (21.1)	N5.1.11 (21.6.5)
  21.3	21.3.15
  21.4	Migrate to 21.5.7
  21.5	21.5.7
  21.6	21.6.4
  21.7	Not vulnerable
  21.8	Not vulnerable
  21.9	Not vulnerable

  Customers with active service contracts can download fixed software releases from the Cisco File Exchange.

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://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180711-staros-dos

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	—	Final	2018-July-11

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