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AUSCERT External Security Bulletin Redistribution
Cisco ACI Multi-Site Orchestrator Application Services
Engine Deployment Authentication Bypass Vulnerability
25 February 2021
AusCERT Security Bulletin Summary
Product: Cisco ACI Multi-Site Orchestrator (MSO)
Publisher: Cisco Systems
Operating System: Cisco
Impact/Access: Administrator Compromise -- Remote/Unauthenticated
Unauthorised Access -- Remote/Unauthenticated
CVE Names: CVE-2021-1388
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Cisco ACI Multi-Site Orchestrator Application Services Engine Deployment
Authentication Bypass Vulnerability
Advisory ID: cisco-sa-mso-authbyp-bb5GmBQv
First Published: 2021 February 24 16:00 GMT
Version 1.0: Final
Workarounds: No workarounds available
Cisco Bug IDs: CSCvw14141
CVE Names: CVE-2021-1388
o A vulnerability in an API endpoint of Cisco ACI Multi-Site Orchestrator
(MSO) installed on the Application Services Engine could allow an
unauthenticated, remote attacker to bypass authentication on an affected
The vulnerability is due to improper token validation on a specific API
endpoint. An attacker could exploit this vulnerability by sending a crafted
request to the affected API. A successful exploit could allow the attacker
to receive a token with administrator-level privileges that could be used
to authenticate to the API on affected MSO and managed Cisco Application
Policy Infrastructure Controller (APIC) devices.
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:
o Vulnerable Products
This vulnerability affects Cisco ACI Multi-Site Orchestrator (MSO) running
a 3.0 release of software only when deployed on a Cisco Application
The MSO can be deployed in the following ways:
MSO cluster in a Cisco Application Services Engine. The MSO software
image can be identified by an 'aci' extension.
MSO nodes deployed as VMs on a Hypervisor. The MSO software image can
be identified by an 'ova' extension.
For more 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.
o There are no workarounds that address this vulnerability.
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
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
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
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
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
In the following table, the left column lists Cisco software releases. The
right column indicates whether a release is affected by the vulnerability
described in this advisory and the first release that includes the fix for
this vulnerability. Customers are advised to upgrade to an appropriate
fixed software release as indicated in this section.
Cisco ACI Multi-Site Orchestrator Software Release First Fixed Release for This Vulnerability
Earlier than 2.2 Not vulnerable
2.2 Not vulnerable
3.0 ^1 3.0(3m)
3.1 Not vulnerable
3.2 Not vulnerable
1. Version 3.0(1i) is not vulnerable. All other 3.0 versions are vulnerable
up to the first fixed release.
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.
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.
| Version | Description | Section | Status | Date |
| 1.0 | Initial public release. | - | Final | 2021-FEB-24 |
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