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AUSCERT External Security Bulletin Redistribution
ESB-2022.0805.2
Cisco Nexus 9000 Series Switches Bidirectional Forwarding
Detection Denial of Service Vulnerability
26 April 2022
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AusCERT Security Bulletin Summary
---------------------------------
Product: Cisco Nexus 9000 Series Switches
Publisher: Cisco Systems
Operating System: Cisco
Resolution: Patch/Upgrade
CVE Names: CVE-2022-20623
Original Bulletin:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-nxos-bfd-dos-wGQXrzxn
Comment: CVSS (Max): 8.6 CVE-2022-20623 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H)
CVSS Source: Cisco Systems
Calculator: https://www.first.org/cvss/calculator/3.1#CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Revision History: April 26 2022: Significant updates to vendor advisory
February 24 2022: Initial Release
- --------------------------BEGIN INCLUDED TEXT--------------------
Cisco Nexus 9000 Series Switches Bidirectional Forwarding Detection Denial of
Service Vulnerability
Priority: High
Advisory ID: cisco-sa-nxos-bfd-dos-wGQXrzxn
First Published: 2022 February 23 16:00 GMT
Last Updated: 2022 March 23 15:41 GMT
Version 1.2: Final
Workarounds: No workarounds available
Cisco Bug IDs: CSCvx75912 CSCwb07349
CVE Names: CVE-2022-20623
CWEs: CWE-399
Summary
o A vulnerability in the rate limiter for Bidirectional Forwarding Detection
(BFD) traffic of Cisco NX-OS Software for Cisco Nexus 9000 Series Switches
could allow an unauthenticated, remote attacker to cause BFD traffic to be
dropped on an affected device.
This vulnerability is due to a logic error in the BFD rate limiter
functionality. An attacker could exploit this vulnerability by sending a
crafted stream of traffic through the device. A successful exploit could
allow the attacker to cause BFD traffic to be dropped, resulting in BFD
session flaps. BFD session flaps can cause route instability and dropped
traffic, resulting in a denial of service (DoS) condition. This
vulnerability applies to both IPv4 and IPv6 traffic.
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-nxos-bfd-dos-wGQXrzxn
This advisory is part of the February 2022 Cisco FXOS and NX-OS Software
Security Advisory Bundled Publication. For a complete list of the
advisories and links to them, see Cisco Event Response: February 2022 Cisco
FXOS and NX-OS Software Security Advisory Bundled Publication .
Affected Products
o Vulnerable Products
This vulnerability affects Cisco Nexus 9000 Series Switches in standalone
NX-OS mode when all of the following conditions are met:
The device is running a vulnerable version of Cisco NX-OS Software.
The device has the BFD feature enabled (BFD is disabled by default).
The device has a Cisco Cloud Scale ASIC installed.
Cisco Nexus 9200 and 9300 Platform Switches
Cisco Nexus 9200 and 9300 Platform Switches are vulnerable from NX-OS
Software release 7.0(3)I6(2) to 7.0(3)I7(3) when using a Cisco Cloud Scale
ASIC. The Cisco Cloud Scale ASIC PIDs ^ 1 supported on these platform
switches are as follows:
N9K-C92160YC-X
N9K-C92300YC
N9K-C92304QC
N9K-C9232C
N9K-C92348GC-X
N9K-C9236C
N9K-C9272Q
N9K-C93108TC-EX
N9K-C93108TC-FX
N9K-C9316D-GX
N9K-C93180LC-EX
N9K-C93180YC2-FX
N9K-C93180YC-EX
N9K-C93180YC-FX
N9K-C93216TC-FX2
N9K-C93240YC-FX2
N9K-C9332C
N9K-C93360YC-FX2
N9K-C9336C-FX2
N9K-C9348GC-FXP
N9K-C93600CD-GX
N9K-C9364C
N9K-C9364C-GX
Cisco Nexus 9500 Series Switches
Cisco Nexus 9500 Series Switches are vulnerable from NX-OS Software release
7.0(3)I6(2) to 9.3(8) and from release 10.1(1) to 10.2(1) when using one of
the following Cisco Cloud Scale ASIC PIDs ^ 1 :
N9K-X97160YC-EX
N9K-X97284YC-FX
N9K-X9732C-EX
N9K-X9732C-FX
N9K-X9736C-EX
N9K-X9736C-FX
N9K-X9788TC-FX
NX-OS Software releases from 10.1(1) to 10.2(2) are also vulnerable when
using the following Cisco GX Cloud Scale ASIC PID ^ 1 :
N9K-X9716D-GX
1. The Cisco Cloud Scale ASIC list of PIDs was accurate at the time of
publication. If there is a specific question about a PID, contact the Cisco
Technical Assistance Center (TAC).
For additional information about which Cisco software releases are
vulnerable, see the Fixed Software section of this advisory.
Determine Vulnerable Hardware
Administrators can issue the show module CLI command to view the PID. In
the following example, the device is vulnerable because the PID is
N9K-C93108TC-FX .
nxos# show module
Mod Ports Module-Type Model Status
--- ----- ------------------------------------- --------------------- ---------
1 54 48x1/10GT + 6x40G/100G Ethernet Modul N9K-C93108TC-FX active *
Determine the BFD Configuration
Step 1: Is the BFD feature enabled
This vulnerability can only be exploited if the BFD feature is enabled on
the device. Administrators can issue the show feature | include bfd CLI
command to check the state of the BFD feature. If BFD displays enabled ,
the feature is enabled on the device.
nxos# show feature | include bfd
bfd 1 enabled
Step 2: Is there an active BFD session
This vulnerability can be exploited as long as there is at least one active
BFD session on the device. Administrators can issue the show bfd neighbors
CLI command to check the state of the BFD sessions. If there is any BFD
session in Up state, the device is considered vulnerable.
nxos# show bfd neighbors
OurAddr NeighAddr LD/RD RH/RS Holdown(mult) State Int Vrf Type
10.10.20.1 10.10.20.2 1090519044/1090519044 Up 5357(3) Up Eth1/1 default SH
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:
Firepower 1000 Series
Firepower 2100 Series
Firepower 4100 Series
Firepower 9300 Security Appliances
MDS 9000 Series Multilayer Switches
Nexus 1000 Virtual Edge for VMware vSphere
Nexus 1000V Switch for Microsoft Hyper-V
Nexus 1000V Switch for VMware vSphere
Nexus 3000 Series Switches
Nexus 5500 Platform Switches
Nexus 5600 Platform Switches
Nexus 6000 Series Switches
Nexus 7000 Series Switches
Nexus 9000 Series Fabric Switches in Application Centric Infrastructure
(ACI) mode
UCS 6200 Series Fabric Interconnects
UCS 6300 Series Fabric Interconnects
UCS 6400 Series Fabric Interconnects
Indicators of Compromise
o To determine if this vulnerability is being exploited on the device,
administrators can issue the show hardware rate-limiter bfd command at the
CLI and review for an excessive amount of Dropped BFD frames.
There are other network events that could cause BFD dropped packets. If
there is a high, consistent rate of increasing BFD Dropped packets
observed, contact the Cisco TAC for further assistance to determine if this
vulnerability is being actively exploited on the device.
nxos# show hardware rate-limiter bfd
Units for Config: kilo bits per second
Allowed, Dropped & Total: aggregated bytes since last clear counters
Module: 1
R-L Class Config Allowed Dropped Total
+----------------+--------------+--------------+--------------+-----------+
bfd 10000 640840 5484530000 5485170840
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 with service contracts that entitle
them to regular software updates should obtain security fixes through their
usual update channels.
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.
The Cisco Support and Downloads page on Cisco.com provides information
about licensing and downloads. This page can also display customer device
support coverage for customers who use the My Devices tool.
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.
Cisco NX-OS Software
To help customers determine their exposure to vulnerabilities in Cisco
NX-OS Software, Cisco provides the Cisco Software Checker to identify any
Cisco Security Advisories that impact a specific Cisco NX-OS Software
release and the earliest release that fixes the vulnerabilities that are
described in each advisory ("First Fixed"). If applicable, the tool also
returns the earliest release that fixes all the vulnerabilities described
in all the advisories identified ("Combined First Fixed").
Customers can use the Cisco Software Checker to search advisories in the
following ways:
Choose the software, platform, and one or more releases
Upload a .txt file that includes a list of specific releases
Enter the output of the show version command
After initiating a search, customers can customize the search to include
all Cisco Security Advisories or one or more specific advisories.
Customers can also use the following form to determine whether a release is
affected by any Cisco Security Advisory by choosing the Cisco NX-OS
Software and platform and then entering a release-for example, 7.0(3)I7(5)
for Cisco Nexus 3000 Series Switches or 14.0(1h) for Cisco NX-OS Software
in ACI mode:
[Cisco NX-OS Software ] [MDS 9000 Series Multilayer Switches]
[ ] [Check]
By default, the Cisco Software Checker includes results only for
vulnerabilities that have a Critical or High Security Impact Rating (SIR).
To include results for Medium SIR vulnerabilities, customers can use the
Cisco Software Checker and check the Medium check box in the drop-down list
under Impact Rating when customizing a search.
Cisco Nexus 9000 Series Switches SMUs
Cisco has released the following SMUs to address this vulnerability.
Customers can download the SMUs from the Software Center on Cisco.com.
Cisco Platform SMU Name
NX-OS
Software
Release
Nexus
7.0(3)I7 9500
(10) Series nxos.CSCvx75912-n9k_ALL-1.0.0-7.0.3.I7.10.lib32_n9000.rpm
Switches
^1
Nexus
9500
9.3(8) Series nxos.CSCvx75912-n9k_ALL-1.0.0-9.3.8.lib32_n9000.rpm
Switches
^1
Nexus
9500
10.2(2) Series nxos64-cs.CSCwb07349-1.0.0-10.2.2.lib32_64_n9000.rpm
Switches
^2
1. Cisco Nexus 9200 and 9300 Platform Switches are not affected when
running this release and do not require an SMU.
2. This SMU is required only if Cisco GX Cloud Scale ASIC PID N9K-X9716D-GX
is in use.
For details about downloading and installing SMUs in Cisco NX-OS Software
for Cisco Nexus 9000 Series Switches, see the Performing Software
Maintenance Upgrades section of the Cisco NX-OS system management
configuration guide Cisco Nexus 9000 Series Switches .
Additional Resources
For help determining the best Cisco NX-OS Software release for a Cisco
Nexus Switch, see the following Recommended Releases documents. If a
security advisory recommends a later release, Cisco recommends following
the advisory guidance.
Cisco MDS Series Switches
Cisco Nexus 1000V for VMware Switch
Cisco Nexus 3000 Series Switches
Cisco Nexus 5500 Platform Switches
Cisco Nexus 5600 Platform Switches
Cisco Nexus 6000 Series Switches
Cisco Nexus 7000 Series Switches
Cisco Nexus 9000 Series Switches
Cisco Nexus 9000 Series ACI-Mode Switches
To determine the best release for Cisco UCS Software, see the Recommended
Releases documents in the release notes for the device.
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.
Related to This Advisory
o Cisco Event Response: February 2022 Semiannual Cisco FXOS and NX-OS
Software Security Advisory Bundled Publication
URL
o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-nxos-bfd-dos-wGQXrzxn
Revision History
o +---------+----------------------------+-----------+--------+-------------+
| Version | Description | Section | Status | Date |
+---------+----------------------------+-----------+--------+-------------+
| | Added bug ID and fix | | | |
| | information specific to | Affected | | |
| | Cisco GX Cloud Scale ASIC | Products, | | |
| 1.2 | PID N9K-X9716D-GX. Updated | Fixed | Final | 2022-MAR-23 |
| | the show command used to | Software | | |
| | verify the active BFD | | | |
| | sessions. | | | |
+---------+----------------------------+-----------+--------+-------------+
| 1.1 | Removed sensitive data in | Affected | Final | 2022-FEB-23 |
| | Affected Products section. | Products | | |
+---------+----------------------------+-----------+--------+-------------+
| 1.0 | Initial public release. | - | Final | 2022-FEB-23 |
+---------+----------------------------+-----------+--------+-------------+
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