Summary

• A vulnerability in the IPv6 implementation of Cisco StarOS could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device.

  The vulnerability is due to insufficient validation of incoming IPv6 traffic. An attacker could exploit this vulnerability by sending a crafted IPv6 packet to an affected device with the goal of reaching the vulnerable section of the input buffer. A successful exploit could allow the attacker to cause the device to reload, resulting in a DoS condition.

  This vulnerability is specific to IPv6 traffic. IPv4 traffic is not affected.

  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-asr5k-ipv6-dos-ce3zhF8m

Affected Products

• Vulnerable Products

  At the time of publication, this vulnerability affected the following Cisco products if they were running a release of Cisco StarOS earlier than Release 21.18.3 and had the Vector Packet Processing (VPP) feature enabled:

  • Cisco ASR 5000 Series Aggregation Services Routers
  • Cisco Virtualized Packet Core-Single Instance (VPC-SI)

  The VPP feature is disabled by default.

  Determine the VPP Configuration

  To see if the VPP feature is enabled, an administrator can use the command show task table process vpp_main all. If the command lists the vpp_main process, then the feature is enabled. The following example shows the output of the show task table process vpp_main all command for a device that has the VPP feature enabled:

  [local]swch# show task table process vpp_main all 
          task                                             parent
   cpu facility                 inst    pid pri node  facility      inst    pid
  ----   ----------------------------------------------  -------------------------
   1/0 vpp_main   1005729   5729   0  all  -                0     0
  
  

  Products Confirmed Not Vulnerable

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

Workarounds

• There are no workarounds that address this vulnerability.

Fixed Software

• When considering software upgrades, customers are advised to regularly consult the advisories for Cisco products, which are available from the Cisco Security Advisories 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.

  Fixed Releases

  At the time of publication, Cisco StarOS releases 21.18.3 and later contained the fix for this vulnerability.

  See the Details section in the bug ID(s) at the top of this advisory for the most complete and current information.

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 Cisco TAC support case.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asr5k-ipv6-dos-ce3zhF8m

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	-	Final	2020-AUG-05

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