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AUSCERT External Security Bulletin Redistribution
ESB-2020.2946
Cisco Nexus 3000 and 9000 Series Switches Privilege
Escalation Vulnerability
27 August 2020
===========================================================================
AusCERT Security Bulletin Summary
---------------------------------
Product: Cisco Nexus 3000 Series Switches
Cisco Nexus 9000 Series Switches
Publisher: Cisco Systems
Operating System: Cisco
Impact/Access: Root Compromise -- Existing Account
Resolution: Patch/Upgrade
CVE Names: CVE-2020-3394
Original Bulletin:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-n3n9k-priv-escal-3QhXJBC
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Cisco Nexus 3000 and 9000 Series Switches Privilege Escalation Vulnerability
Priority: High
Advisory ID: cisco-sa-n3n9k-priv-escal-3QhXJBC
First Published: 2020 August 26 16:00 GMT
Last Updated: 2020 August 26 20:59 GMT
Version 1.1: Final
Workarounds: Yes
Cisco Bug IDs: CSCvt77885
CVE-2020-3394
CWE-285
CVSS Score:
7.8 AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:X/RL:X/RC:X
Summary
o A vulnerability in the Enable Secret feature of Cisco Nexus 3000 Series
Switches and Cisco Nexus 9000 Series Switches in standalone NX-OS mode
could allow an authenticated, local attacker to issue the enable command
and get full administrative privileges. To exploit this vulnerability, the
attacker would need to have valid credentials for the affected device.
The vulnerability is due to a logic error in the implementation of the
enable command. An attacker could exploit this vulnerability by logging in
to the device and issuing the enable command. A successful exploit could
allow the attacker to gain full administrative privileges without using the
enable password.
Note: The Enable Secret feature is disabled by default.
Cisco has released software updates that address this vulnerability. There
are workarounds that address this vulnerability.
This advisory is available at the following link:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/
cisco-sa-n3n9k-priv-escal-3QhXJBC
This advisory is part of the August 2020 Cisco FXOS and NX-OS Software
Security Advisory Bundled Publication, which includes seven Cisco Security
Advisories that describe seven vulnerabilities. For a complete list of the
advisories and links to them, see Cisco Event Response: August 2020 Cisco
FXOS and NX-OS Software Security Advisory Bundled Publication .
Affected Products
o Vulnerable Products
This vulnerability affects the following Cisco products if they are running
a vulnerable release of Cisco NX-OS Software and have the feature privilege
command and the enable secret command configured:
Nexus 3000 Series Switches
Nexus 9000 Series Switches in standalone NX-OS mode
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:
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 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
Details
o The enable secret command was added to Cisco NX-OS Software as a tool for
migrating configurations from Cisco IOS Software to Cisco NX-OS Software
only. The command serves no other purpose in Cisco NX-OS Software and
should otherwise be disabled. The enable secret command will be removed in
future releases.
The enable secret command is used in Cisco IOS Software to set a password
that grants a user privileged administrative access to a Cisco IOS Software
system. In Cisco NX-OS Software, there is no concept of an enable-secret or
enable-password setting. Privileges are managed using role-based access
control (RBAC). The functional equivalent to enabling mode access on a
Cisco IOS Software device is assignment of an account to the network-admin
(global privileged access) or vdc-admin (virtual device context [VDC]
-specific privileged access) role in Cisco NX-OS Software.
For additional information, see the Cisco Guide to Securing NX-OS Software
Devices .
Indicators of Compromise
o To determine whether this vulnerability has been exploited, use the show
accounting log | include "enable" command. The following example shows the
output of this command after a low-privileged user has elevated their
privilege by using the enable command:
nxos# show accounting log | include "enable"
type=update:id=console0:user=guest:cmd=enable (SUCCESS)
type=update:id=console0:user=guest:cmd=enable 15 (SUCCESS)
Workarounds
o There is a workaround that addresses this vulnerability.
Cisco NX-OS Software uses RBAC to manage user accounts and privileges. For
guidance, see the Configuring User Accounts and RBAC section of the Cisco
NX-OS Security Configuration Guide.
Once RBAC is configured, remove the enable secret command from the
configuration.
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.
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, 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: August 2020 Cisco FXOS and NX-OS Software Security
Advisory Bundled Publication
URL
o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/
cisco-sa-n3n9k-priv-escal-3QhXJBC
Revision History
o +---------+-------------------------+--------------+--------+-------------+
| Version | Description | Section | Status | Date |
+---------+-------------------------+--------------+--------+-------------+
| 1.1 | Fixed Software Checker | Fixed | Final | 2020-AUG-26 |
| | link. | Software | | |
+---------+-------------------------+--------------+--------+-------------+
| 1.0 | Initial public release. | - | Final | 2020-AUG-26 |
+---------+-------------------------+--------------+--------+-------------+
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