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AUSCERT External Security Bulletin Redistribution
ESB-2020.3999.4
Cisco IOS XR Software for Cisco ASR 9000 Series Aggregation Services
Routers Slow Path Forwarding Denial of Service Vulnerability
17 November 2020
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AusCERT Security Bulletin Summary
---------------------------------
Product: Cisco IOS XR
Publisher: Cisco Systems
Operating System: Cisco
Impact/Access: Denial of Service -- Remote/Unauthenticated
Resolution: Patch/Upgrade
CVE Names: CVE-2020-26070
Original Bulletin:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-xr-cp-dos-ej8VB9QY
Revision History: November 17 2020: Vendor added further SMU information
November 16 2020: Vendor released summary update
November 12 2020: Vendor added SMU information
November 11 2020: Initial Release
- --------------------------BEGIN INCLUDED TEXT--------------------
Cisco IOS XR Software for Cisco ASR 9000 Series Aggregation Services Routers
Slow Path Forwarding Denial of Service Vulnerability
Priority: High
Advisory ID: cisco-sa-xr-cp-dos-ej8VB9QY
First Published: 2020 November 10 16:00 GMT
Last Updated: 2020 November 16 15:29 GMT
Version 1.3: Final
Workarounds: No workarounds available
Cisco Bug IDs: CSCvv09115
CVE Names: CVE-2020-26070
CWEs: CWE-404
Summary
o A vulnerability in the egress packet processing function of Cisco IOS XR
Software for Cisco ASR 9000 Series Aggregation Services 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://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/
cisco-sa-xr-cp-dos-ej8VB9QY
Affected Products
o Vulnerable Products
This vulnerability affects Cisco ASR 9000 Series Aggregation Services
Routers if they are running a Cisco IOS XR Software release earlier than
releases 6.7.2 or 7.1.2.
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 Router
NX-OS Software
Indicators of Compromise
o 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
o There are no workarounds that address this vulnerability.
Fixed Software
o 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.
Fixed Releases
Cisco fixed this vulnerability in Cisco IOS XR Software releases 6.7.2 and
later and releases 7.1.2 and later.
Cisco has released software maintenance upgrades (SMUs) to address this
vulnerability. Customers are advised to install the appropriate SMU as
shown in the following tables. Customers who require SMUs for other
platforms and releases 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
6.3.3 asr9k-px-6.3.3.CSCvv09115
6.4.2 asr9k-px-6.4.2.CSCvv09115
6.5.3 asr9k-px-6.5.3.CSCvv09115
ASR9K-X64
Cisco IOS XR Software Release SMU Name
6.5.3 asr9k-x64-6.5.3.CSCvv09115
Exploitation and Public Announcements
o 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
o This vulnerability was found during the resolution of a Cisco TAC support
case.
Cisco Security Vulnerability Policy
o 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.
URL
o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/
cisco-sa-xr-cp-dos-ej8VB9QY
Revision History
o +---------+------------------------+---------------+--------+-------------+
| Version | Description | Section | Status | Date |
+---------+------------------------+---------------+--------+-------------+
| | Added SMU information. | Fixed | | |
| 1.3 | Updated the release | Software and | Final | 2020-NOV-16 |
| | date for version 1.2. | Revision | | |
| | | History | | |
+---------+------------------------+---------------+--------+-------------+
| 1.2 | Summary update. | Summary | Final | 2020-NOV-13 |
+---------+------------------------+---------------+--------+-------------+
| 1.1 | Added SMU information. | Fixed | Final | 2020-NOV-11 |
| | | Software | | |
+---------+------------------------+---------------+--------+-------------+
| 1.0 | Initial public | - | Final | 2020-NOV-10 |
| | release. | | | |
+---------+------------------------+---------------+--------+-------------+
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