Cisco Security Advisory
Cisco IOS XR Software for ASR 9000 Series Routers Denial of Service Vulnerability
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CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H/E:X/RL:X/RC:X
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A vulnerability in the Layer 2 punt code of Cisco IOS XR Software running on Cisco ASR 9000 Series Aggregation Services Routers could allow an unauthenticated, adjacent attacker to cause the affected line card to reboot.
This vulnerability is due to incorrect handling of specific Ethernet frames that cause a spin loop that can make the network processors unresponsive. An attacker could exploit this vulnerability by sending specific types of Ethernet frames on the segment where the affected line cards are attached. A successful exploit could allow the attacker to cause the affected line card to reboot.
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-npspin-QYpwdhFDThis advisory is part of the September 2021 release of the Cisco IOS XR Software Security Advisory Bundled Publication. For a complete list of the advisories and links to them, see Cisco Event Response: September 2021 Cisco IOS XR Software Security Advisory Bundled Publication.
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Vulnerable Products
This vulnerability affects Cisco IOS XR Software when all the following conditions apply:
- The Cisco IOS XR Software release is Release 6.4.0 or later but earlier than a first fixed release.
- The software is running on Cisco ASR 9000 Series Aggregation Services Routers.
- These routers have either a Typhoon or Tomahawk Ethernet line card installed.
To determine which line cards are installed in the device, use the show platform command at the CLI.
The following line cards are Typhoon based:
- A9K-1X100GE-SE
- A9K-1X100GE-TR
- A9K-24X10GE-SE
- A9K-24X10GE-TR
- A9K-2X100GE-SE
- A9K-2X100GE-TR
- A9K-36X10GE-SE
- A9K-36X10GE-TR
- A9K-40GE-SE
- A9K-40GE-TR
- A9K-4T16GE-SE
- A9K-4T16GE-TR
- A9K-MOD160-SE
- A9K-MOD160-TR
- A9K-MOD80-SE
- A9K-MOD80-TR
Note: Cisco ASR 9001 and ASR 9001-S Routers have Typhoon-based line cards built into the standalone chassis.
The following line cards are Tomahawk based:
- A99-12X100GE
- A99-12X100GE-CM
- A99-48X10GE-1G-SE
- A99-48X10GE-1G-TR
- A99-8X100GE-CM
- A99-8X100GE-SE
- A99-8X100GE-TR
- A9K-24X10GE-1G-CM
- A9K-24X10GE-1G-SE
- A9K-24X10GE-1G-TR
- A9K-400G-DWDM-TR
- A9K-48X10GE-1G-CM
- A9K-48X10GE-1G-SE
- A9K-48X10GE-1G-TR
- A9K-4X100GE
- A9K-4X100GE-SE
- A9K-4X100GE-TR
- A9K-8X100GE-CM
- A9K-8X100GE-SE
- A9K-8X100GE-TR
- A9K-8X100G-LB-SE
- A9K-8X100G-LB-TR
- A9K-MOD200-SE
- A9K-MOD200-TR
- A9K-MOD400-CM
- A9K-MOD400-SE
- A9K-MOD400-TR
For additional information about line card type identification, see ASR 9000 Series Line Card Types.
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:
- IOS Software
- IOS XE Software
- IOS XRv 9000 Routers
- NX-OS Software
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There are no workarounds that address this vulnerability.
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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.htmlAdditionally, 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.
Fixed Releases
In the following table(s), the left column lists Cisco software releases. The right column indicates whether a release is affected by the vulnerability described in this advisory and the first release that includes the fix for this vulnerability. Customers are advised to upgrade to an appropriate fixed software release as indicated in this section.
Cisco IOS XR Software Release First Fixed Release for This Vulnerability Earlier than 6.4 Not vulnerable. 6.4 Vulnerable; migrate to a fixed release. 6.5 Vulnerable; migrate to a fixed release. 6.6 6.6.3 6.7 6.7.1 7.0 7.0.2 7.1 7.1.1 7.2 and later Not affected. Cisco has 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.
Cisco IOS XR Software Release Platform SMU Name 6.4.2 ASR9K-X64 asr9k-x64-6.4.2.CSCvq33187 6.5.3 ASR9K-X64
ASR9K-PXasr9k-x64-6.5.3.CSCvq33187
asr9k-px-6.5.3.CSCvq33187The Cisco Product Security Incident Response Team (PSIRT) validates only the affected and fixed release information that is documented in this advisory.
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The Cisco PSIRT is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.
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This vulnerability was found during the resolution of a Cisco TAC support case.
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To learn about Cisco security vulnerability disclosure policies and publications, see the Security Vulnerability Policy. This document also contains instructions for obtaining fixed software and receiving security vulnerability information from Cisco.
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Show LessVersion Description Section Status Date 1.1 Updated SMU information. Fixed Software Final 2021-OCT-08 1.0 Initial public release. - Final 2021-SEP-08
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