Protect yourself against future threats.
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256
===========================================================================
AUSCERT External Security Bulletin Redistribution
ESB-2020.0710
Cisco Nexus 1000V Switch for VMware vSphere Secure Login
Enhancements Denial of Service Vulnerability
28 February 2020
===========================================================================
AusCERT Security Bulletin Summary
---------------------------------
Product: Cisco Nexus 1000V Switch
Publisher: Cisco Systems
Operating System: Cisco
Virtualisation
Impact/Access: Denial of Service -- Remote/Unauthenticated
Resolution: Patch/Upgrade
CVE Names: CVE-2020-3168
Original Bulletin:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20200226-nexus-1000v-dos
- --------------------------BEGIN INCLUDED TEXT--------------------
Cisco Nexus 1000V Switch for VMware vSphere Secure Login Enhancements Denial of
Service Vulnerability
Priority: High
Advisory ID: cisco-sa-20200226-nexus-1000v-dos
First Published: 2020 February 26 16:00 GMT
Version 1.0: Final
Workarounds: No workarounds available
Cisco Bug IDs: CSCvp26722
CVE-2020-3168
CWE-399
CVSS Score:
7.5 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:X/RL:X/RC:X
Summary
o A vulnerability in the Secure Login Enhancements capability of Cisco Nexus
1000V Switch for VMware vSphere could allow an unauthenticated, remote
attacker to cause an affected Nexus 1000V Virtual Supervisor Module (VSM)
to become inaccessible to users through the CLI.
The vulnerability is due to improper resource allocation during failed CLI
login attempts when login parameters that are part of the Secure Login
Enhancements capability are configured on an affected device. An attacker
could exploit this vulnerability by performing a high amount of login
attempts against the affected device. A successful exploit could cause the
affected device to become inaccessible to other users, resulting in a
denial of service (DoS) condition requiring a manual power cycle of the VSM
to recover.
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-20200226-nexus-1000v-dos
This advisory is part of the February 2020 Cisco FXOS and NX-OS Software
Security Advisory Bundled Publication, which includes six Cisco Security
Advisories that describe six vulnerabilities. For a complete list of the
advisories and links to them, see Cisco Event Response: February 2020 Cisco
FXOS and NX-OS Software Security Advisory Bundled Publication .
Affected Products
o Vulnerable Products
This vulnerability affects the Cisco Nexus 1000V Switch for VMware vSphere
Virtual Supervisor Module (VSM) if it is running Cisco NX-OS Software
Release 5.2(1)SV3(4.1a) and has been configured with login parameters that
are part of the Secure Login Enhancements capability of the device.
Administrators can determine whether the login parameters of the Secure
Login Enhancements capability are configured on a device by using the show
running-config | include "login block-for" command in the device CLI. The
following example shows the output of the command for a device that is
configured with login parameters:
switch# show running-config | include "login block-for"
login block-for 120 attempts 10 within 60
If the command does not return any output, no affected configuration is
present, and the device is not vulnerable.
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 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
Nexus 9000 Series Switches in standalone NX-OS mode
UCS 6200 Series Fabric Interconnects
UCS 6300 Series Fabric Interconnects
UCS 6400 Series Fabric Interconnects
Details
o The Secure Login Enhancements capability of Cisco Nexus 1000V Switch for
VMware vSphere has been added in Cisco NX-OS Software Release 5.2(1)SV3
(4.1a) and allows the configuration of login parameters that can
temporarily block login attempts when a suspected DoS attack is detected.
This capability can slow down dictionary attacks by enforcing a quiet
period when multiple failed login attempts are detected.
All login parameters are disabled by default. If no login parameter is
configured, the device is not affected by the vulnerability described in
this security advisory.
Further information about Secure Login Enhancements is available in the
Cisco Nexus 1000V for VMware vSphere Security Configuration Guide .
Indicators of Compromise
o Exploitation of this vulnerability requires a high amount of failed CLI
login attempts against an affected device. Administrators may identify
failed login attempts by using the show login failures CLI command, or by
looking for repeated Authentication failed log messages similar to the
following:
2020 Feb 13 17:58:32 switch %AUTHPRIV-3-SYSTEM_MSG: pam_aaa:Authentication failed for user xxx from ...
For failed login attempts made through SSH, the source IP address of the
SSH connection is reported in the Authentication failed log message, as
well as in the output of the show login failures CLI command, and can be
used to identify eventual attackers. The source IP address is not reported
for login attempts made through Telnet. Telnet connections to the device
are disabled by default.
A successful exploitation of this vulnerability would cause the CLI login
process to start failing to authenticate any user, generating error
messages similar to the following:
2020 Feb 13 18:18:03 switch %AUTHPRIV-3-SYSTEM_MSG: PAM _pam_init_handlers: no default config /etc/pam.d/other - aaad
2020 Feb 13 18:18:03 switch %AUTHPRIV-3-SYSTEM_MSG: PAM error reading PAM configuration file - aaad
2020 Feb 13 18:18:03 switch %AUTHPRIV-3-SYSTEM_MSG: PAM pam_start: failed to initialize handlers - aaad
2020 Feb 13 18:18:03 switch %AUTHPRIV-3-SYSTEM_MSG: pam_aaa:Authentication failed for user xxx from ...
Customers are advised to contact their support organization to review the
error messages and determine whether the vulnerability has been exploited
on the device.
Workarounds
o There are no workarounds that address this vulnerability.
Customers who cannot immediately apply a software fix may evaluate the
possibility of disabling Secure Login Enhancements by removing the login
parameters from the configuration until a software fix can be applied, and
relying on an access control list (ACL) on the management interface (mgmt0)
to restrict access to the device only from explicitly trusted source IP
addresses.
Customers should first evaluate the impact of those configuration changes
to the device and their security policy. Customers concerned about
undesired or unexpected side effects should consult with their support
organization before implementing any configuration change.
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 and Alerts 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.
Additional Resources
For help determining the best Cisco NX-OS Software release for a Cisco
Nexus Switch, administrators can refer to 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, 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 internal security testing.
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 2020 Cisco FXOS and NX-OS Software Security
Advisory Bundled Publication
URL
o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/
cisco-sa-20200226-nexus-1000v-dos
Revision History
o +---------+-------------------------+---------+--------+------------------+
| Version | Description | Section | Status | Date |
+---------+-------------------------+---------+--------+------------------+
| 1.0 | Initial public release. | - | Final | 2020-February-26 |
+---------+-------------------------+---------+--------+------------------+
- --------------------------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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=xgn2
-----END PGP SIGNATURE-----