Protect yourself against future threats.
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256
===========================================================================
AUSCERT External Security Bulletin Redistribution
ESB-2021.0708
Cisco FXOS and NX-OS Software Unidirectional Link Detection Denial of
Service and Arbitrary Code Execution Vulnerability
25 February 2021
===========================================================================
AusCERT Security Bulletin Summary
---------------------------------
Product: Cisco FXOS and NX-OS Software
Publisher: Cisco Systems
Operating System: Cisco
Impact/Access: Administrator Compromise -- Remote/Unauthenticated
Execute Arbitrary Code/Commands -- Remote/Unauthenticated
Denial of Service -- Remote/Unauthenticated
Resolution: Patch/Upgrade
CVE Names: CVE-2021-1368
Original Bulletin:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-nxos-udld-rce-xetH6w35
- --------------------------BEGIN INCLUDED TEXT--------------------
Cisco FXOS and NX-OS Software Unidirectional Link Detection Denial of Service
and Arbitrary Code Execution Vulnerability
Priority: Medium
Advisory ID: cisco-sa-nxos-udld-rce-xetH6w35
First Published: 2021 February 24 16:00 GMT
Version 1.0: Final
Workarounds: No workarounds available
Cisco Bug IDs: CSCvv78238 CSCvv96088 CSCvv96090 CSCvv96092 CSCvv96107
CSCvw38964 CSCvw38981 CSCvw38982 CSCvw38983 CSCvw38984
CSCvw38995 CSCvw45654
CVE Names: CVE-2021-1368
CWEs: CWE-787
Summary
o A vulnerability in the Unidirectional Link Detection (UDLD) feature of
Cisco FXOS Software and Cisco NX-OS Software could allow an
unauthenticated, adjacent attacker to execute arbitrary code with
administrative privileges or cause a denial of service (DoS) condition on
an affected device.
This vulnerability is due to insufficient input validation. An attacker
could exploit this vulnerability by sending crafted Cisco UDLD protocol
packets to a directly connected, affected device. A successful exploit
could allow the attacker to execute arbitrary code with administrative
privileges or cause the Cisco UDLD process to crash and restart multiple
times, causing the affected device to reload and resulting in a DoS
condition.
Note: The UDLD feature is disabled by default, and the conditions to
exploit this vulnerability are strict. The attacker needs full control of a
directly connected device. That device must be connected over a port
channel that has UDLD enabled. To trigger arbitrary code execution, both
the UDLD-enabled port channel and specific system conditions must exist. In
the absence of either the UDLD-enabled port channel or the system
conditions, attempts to exploit this vulnerability will result in a DoS
condition.
It is possible, but highly unlikely, that an attacker could control the
necessary conditions for exploitation. The CVSS score reflects this
possibility. However, given the complexity of exploitation, Cisco has
assigned a Medium Security Impact Rating (SIR) to this vulnerability.
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-udld-rce-xetH6w35
Affected Products
o Vulnerable Products
At the time of publication, this vulnerability affected the following Cisco
products if they were running a vulnerable release of Cisco FXOS or NX-OS
Software and had the UDLD feature enabled:
Firepower 4100 Series ( CSCvv96092 / CSCvw38984 ) ^ 1
Firepower 9300 Security Appliances ( CSCvv96092 / CSCvw38984 ) ^ 1
MDS 9000 Series Multilayer Switches ( CSCvv96088 / CSCvw38981 )
Nexus 3000 Series Switches ( CSCvv78238 / CSCvw38964 )
Nexus 5500 Platform Switches ( CSCvv96090 / CSCvw38982 )
Nexus 5600 Platform Switches ( CSCvv96090 / CSCvw38982 )
Nexus 6000 Series Switches ( CSCvv96090 / CSCvw38982 )
Nexus 7000 Series Switches ( CSCvv96088 / CSCvw38981 )
Nexus 9000 Series Switches in standalone NX-OS mode ( CSCvv78238 /
CSCvw38964 )
UCS 6200 Series Fabric Interconnects ( CSCvw45654 )
UCS 6300 Series Fabric Interconnects ( CSCvw38983 )
UCS 6400 Series Fabric Interconnects ( CSCvv96107 / CSCvw38995 )
1. Firepower 4100/9300 products do not officially support UDLD; however,
the CLI includes commands to enable it. These products could be vulnerable
only if UDLD has been enabled in error. In such cases, administrators are
advised to disable UDLD to fully eliminate exposure to this vulnerability.
For information about which Cisco software releases were vulnerable at the
time of publication, see the Fixed Software section of this advisory. See
the Details section in the bug ID(s) at the top of this advisory for the
most complete and current information.
Determine the Status of the UDLD Feature on Affected Devices
Devices that are running a vulnerable software release and have the UDLD
feature enabled are affected by this vulnerability. The following
subsections provide details about how to determine whether the UDLD feature
is enabled.
Cisco FXOS Software and UCS Fabric Interconnects
To determine whether the UDLD feature is enabled on a device, use the scope
org command followed by the show udld-link-policy commands at the device
CLI. The command output will display either Enabled or Disabled under Admin
State for the default and for any manually configured UDLD link policy. The
following example shows the command output on a device that has UDLD
disabled:
fxos# scope org
fxos# show udld-link-policy
UDLD link policy:
Name Admin State UDLD mode
---------- ----------- ---------
default Disabled Normal
Cisco NX-OS Software
To determine whether the UDLD feature is enabled on a device, use the show
running-config | include "feature udld" command at the device CLI. If the
command returns output, the udld feature is configured on the device. The
following example shows the command output on a device that has UDLD
enabled:
nxos# show running-config | include "feature udld"
feature udld
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
Nexus 1000 Virtual Edge for VMware vSphere
Nexus 1000V Switch for Microsoft Hyper-V
Nexus 1000V Switch for VMware vSphere
Nexus 9000 Series Fabric Switches in Application Centric Infrastructure
(ACI) mode
Workarounds
o There are no workarounds that address this vulnerability.
Fixed Software
o 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.
Cisco FXOS Software
At the time of publication, the release information in the following table
(s) was accurate. See the Details section in the bug ID(s) at the top of
this advisory for the most complete and current information.
The left column lists Cisco software releases, and the right column
indicates whether a release was affected by the vulnerability described in
this advisory and which release included the fix for this vulnerability.
Firepower 4100 Series and Firepower 9300 Security Appliances
Cisco FXOS Software Release First Fixed Release for This Vulnerability
Earlier than 2.8 Migrate to a fixed release. ^1
2.8 2.8.1.143 ^1
2.9 2.9.1.135 ^1
1. Firepower 4100/9300 products do not officially support UDLD; however,
the CLI includes commands to enable it. These products could be vulnerable
only if UDLD has been enabled in error. In such cases, administrators are
advised to disable UDLD to fully eliminate exposure to this vulnerability.
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.
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 3000 and 9000 Series Switches SMUs
For Cisco Nexus 3000 and 9000 Series Switches, SMUs are available for Cisco
NX-OS Software. Customers can download the following SMUs from the Software
Center on Cisco.com:
Release 7.0(3)I7(8):
nxos.CSCvv78238-n9k_ALL-1.0.0-7.0.3.I7.8.lib32_n9000.rpm
Release 7.0(3)I7(9):
nxos.CSCvv78238-n9k_ALL-1.0.0-7.0.3.I7.9.lib32_n9000.rpm
For details about downloading and installing SMUs in Cisco NX-OS Software
for Cisco Nexus 3000 and 9000 Series Switches, see the Performing Software
Maintenance Upgrades section of the appropriate Cisco NX-OS system
management configuration guide:
Cisco Nexus 3000 Series Switches
Cisco Nexus 9000 Series Switches
See the Details section in the bug ID(s) at the top of this advisory for
the most complete and current information.
Cisco Nexus 7000 Series Switches SMUs
For Cisco Nexus 7000 Series Switches, SMUs are available for Cisco NX-OS
Software Release 8.2(6). Customers can download the following SMUs from the
Software Center on Cisco.com:
n7000-s2-dk9.8.2.6.CSCvx15395.bin
n7700-s2-dk9.8.2.6.CSCvx15395.bin
For details about downloading and installing SMUs in Cisco NX-OS Software
for Cisco Nexus 7000 Series Switches, see the Performing Software
Maintenance Upgrades section of the Cisco Nexus 7000 Series NX-OS System
Management Configuration Guide .
See the Details section in the bug ID(s) at the top of this advisory for
the most complete and current information.
Cisco UCS Software
At the time of publication, the release information in the following table
(s) was accurate. See the Details section in the bug ID(s) at the top of
this advisory for the most complete and current information.
The left column lists Cisco software releases, and the right column
indicates whether a release was affected by the vulnerability described in
this advisory and which release included the fix for this vulnerability.
UCS 6200, 6300, and 6400 Series Fabric Interconnects
Cisco UCS Software Release First Fixed Release for This Vulnerability
Earlier than 4.0 Migrate to a fixed release.
4.0 4.0(4l)
4.1 4.1(2c)
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.
URL
o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-nxos-udld-rce-xetH6w35
Revision History
o +----------+---------------------------+----------+--------+--------------+
| Version | Description | Section | Status | Date |
+----------+---------------------------+----------+--------+--------------+
| 1.0 | Initial public release. | - | Final | 2021-FEB-24 |
+----------+---------------------------+----------+--------+--------------+
- --------------------------END INCLUDED TEXT--------------------
You have received this e-mail bulletin as a result of your organisation's
registration with AusCERT. The mailing list you are subscribed to is
maintained within your organisation, so if you do not wish to continue
receiving these bulletins you should contact your local IT manager. If
you do not know who that is, please send an email to auscert@auscert.org.au
and we will forward your request to the appropriate person.
NOTE: Third Party Rights
This security bulletin is provided as a service to AusCERT's members. As
AusCERT did not write the document quoted above, AusCERT has had no control
over its content. The decision to follow or act on information or advice
contained in this security bulletin is the responsibility of each user or
organisation, and should be considered in accordance with your organisation's
site policies and procedures. AusCERT takes no responsibility for consequences
which may arise from following or acting on information or advice contained in
this security bulletin.
NOTE: This is only the original release of the security bulletin. It may
not be updated when updates to the original are made. If downloading at
a later date, it is recommended that the bulletin is retrieved directly
from the author's website to ensure that the information is still current.
Contact information for the authors of the original document is included
in the Security Bulletin above. If you have any questions or need further
information, please contact them directly.
Previous advisories and external security bulletins can be retrieved from:
https://www.auscert.org.au/bulletins/
===========================================================================
Australian Computer Emergency Response Team
The University of Queensland
Brisbane
Qld 4072
Internet Email: auscert@auscert.org.au
Facsimile: (07) 3365 7031
Telephone: (07) 3365 4417 (International: +61 7 3365 4417)
AusCERT personnel answer during Queensland business hours
which are GMT+10:00 (AEST).
On call after hours for member emergencies only.
===========================================================================
-----BEGIN PGP SIGNATURE-----
Comment: http://www.auscert.org.au/render.html?it=1967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=hg3J
-----END PGP SIGNATURE-----