Summary

• A vulnerability in the egress packet processing function of Cisco IOS XR Software for Cisco ASR 9000 Series Aggregation Services Routers and Cisco Network Convergence System (NCS) 5000 Series Routers could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device.

  The vulnerability is due to improper resource allocation when an affected device processes network traffic in software switching mode. An attacker could exploit this vulnerability by sending specific streams of Layer 2 or Layer 3 protocol data units (PDUs) to an affected device. A successful exploit could cause the affected device to run out of buffer resources, which could make the device unable to process or forward traffic, resulting in a DoS condition. The device would need to be restarted to regain functionality.

  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-xr-cp-dos-ej8VB9QY

Affected Products

• Vulnerable Products

  This vulnerability affects Cisco ASR 9000 Series Aggregation Services Routers and Cisco NCS 5000 Series Routers if they are running a vulnerable release of Cisco IOS XR Software.

  For information about which Cisco software releases are vulnerable, see the Fixed Software section of 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 the following Cisco products:

  • Carrier Routing System (CRS)
  • IOS Software
  • IOS XE Software
  • IOS XRv 9000 Router
  • Network Convergence System (NCS) 520 Series Routers
  • NCS 540 Series Routers
  • NCS 560 Series Routers
  • NCS 5500 Series
  • NCS 6000 Series Routers
  • NX-OS Software

Indicators of Compromise

• Exploitation of this vulnerability can result in the exhaustion of buffer resources. When a device is experiencing buffer resources exhaustion, the following message may be seen in the system logs:

  %PKT_INFRA-spp-4-PKT_ALLOC_FAIL : Failed to allocate n packets for sending

  This error message indicates that the device is not able to allocate buffer resources and forward network traffic in software switching mode. However, buffer resource exhaustion may happen for a reason other than the exploitation of this vulnerability. Customers are advised to contact their support organization to review the error messages and determine whether the device has been compromised by an exploitation of this vulnerability.

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 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.

  ASR 9000 Series Aggregation Services Routers: CSCvv09115

  Cisco fixed this vulnerability in Cisco IOS XR Software releases 6.7.2, 7.1.2, and 7.1.3.

  NCS 5000 Series Routers: CSCvw46865

  Cisco fixed this vulnerability in Cisco IOS XR Software Release 7.1.3.

  Cisco also released the following SMUs to address this vulnerability. Customers who require SMUs for platforms or releases that are not listed are advised to contact their support organization.

  The following tables provide the SMU name for each release based on platform.

  ASR9K-PX

  Cisco IOS XR Software Release	SMU Name
  5.3.2	asr9k-px-5.3.2.CSCvv09115
  5.3.3	asr9k-px-5.3.3.CSCvv09115
  5.3.4	asr9k-px-5.3.4.CSCvv09115
  6.1.4	asr9k-px-6.1.4.CSCvv09115
  6.2.1	asr9k-px-6.2.1.CSCvv09115
  6.2.2	asr9k-px-6.2.2.CSCvv09115
  6.2.3	asr9k-px-6.2.3.CSCvv09115
  6.3.2	asr9k-px-6.3.2.CSCvv09115
  6.3.3	asr9k-px-6.3.3.CSCvv09115
  6.4.2	asr9k-px-6.4.2.CSCvv09115
  6.5.2	asr9k-px-6.5.2.CSCvv09115
  6.5.3	asr9k-px-6.5.3.CSCvv09115
  6.6.2	asr9k-px-6.6.2.CSCvv09115
  6.6.3	asr9k-px-6.6.3.CSCvv09115

  ASR9K-X64

  Cisco IOS XR Software Release	SMU Name
  6.2.3	asr9k-x64-6.2.3.CSCvv09115
  6.3.3	asr9k-x64-6.3.3.CSCvv09115
  6.4.1	asr9k-x64-6.4.1.CSCvv09115
  6.4.2	asr9k-x64-6.4.2.CSCvv09115
  6.5.3	asr9k-x64-6.5.3.CSCvv09115
  6.6.2	asr9k-x64-6.6.2.CSCvv09115
  6.6.3	asr9k-x64-6.6.3.CSCvv09115
  7.0.2	asr9k-x64-7.0.2.CSCvv09115
  7.1.15	asr9k-x64-7.1.15.CSCvv09115

  NCS5K

  Cisco IOS XR Software Release	SMU Name
  6.5.3	ncs5k-6.5.3.CSCvw46865
  6.6.3	ncs5k-6.6.3.CSCvw46865
  7.1.2	ncs5k-7.1.2.CSCvw46865

  
  

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-xr-cp-dos-ej8VB9QY

Revision History

• Version	Description	Section	Status	Date
  2.0	Added Cisco Network Convergence System (NCS) 5000 Series Routers as an affected product. Added products that have been confirmed not vulnerable. Added fixed software and SMU releases for Cisco NCS 5000 Series Routers.	Title, Header, Summary, Vulnerable Products, Products Confirmed Not Vulnerable, Fixed Software	Final	2021-FEB-10
  1.5	Added SMU information.	Fixed Software	Final	2020-DEC-01
  1.4	Added SMU information.	Fixed Software	Final	2020-NOV-30
  1.3	Added SMU information. Updated the release date for version 1.2.	Fixed Software and Revision History	Final	2020-NOV-16
  1.2	Summary update.	Summary	Final	2020-NOV-13
  1.1	Added SMU information.	Fixed Software	Final	2020-NOV-11
  1.0	Initial public release.	-	Final	2020-NOV-10

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