How severe is CVE-2021-1388?

CVE-2021-1388 has a CVSS 3.x base score of 10.0, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-1388 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 14% (96th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-1388?

CVE-2021-1388 primarily affects Cisco Aci Multi-site Orchestrator. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-1388?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2021-1388 published?

CVE-2021-1388 was published on 2021-02-24 and last updated on 2026-06-17.

CVE-2021-1388

CVE-2021-1388 is a critical-severity vulnerability in Cisco Aci Multi-site Orchestrator with a CVSS 3.x base score of 10.0. Its EPSS exploit-prediction score of 14% places it in the 96th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-269.

Key facts

Severity: Critical (CVSS 3.x base score 10.0)
CVSS v2: 9.3
EPSS exploit prediction: 14% (96th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-269
Affected product: Cisco Aci Multi-site Orchestrator
Published: 2021-02-24
Last modified: 2026-06-17

Description

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 device. 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.

Frequently asked questions

What is CVE-2021-1388?: 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 device. 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.
How severe is CVE-2021-1388?: CVE-2021-1388 has a CVSS 3.x base score of 10.0, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-1388 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 14% (96th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-1388?: CVE-2021-1388 primarily affects Cisco Aci Multi-site Orchestrator. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-1388?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-1388 published?: CVE-2021-1388 was published on 2021-02-24 and last updated on 2026-06-17.

References

https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-mso-authbyp-bb5GmBQv

Affected products (2)

cpe:2.3:a:cisco:aci_multi-site_orchestrator:*:*:*:*:*:*:*:*
cpe:2.3:a:cisco:application_policy_infrastructure_controller:3.0\(3i\):*:*:*:*:*:*:*

More vulnerabilities in Cisco Aci Multi-site Orchestrator

CVE-2022-20921 — High (CVSS 8.8): A vulnerability in the API implementation of Cisco ACI Multi-Site Orchestrator (MSO) could allow an authenticated,…

All CVEs affecting Cisco Aci Multi-site Orchestrator →

Other CWE-269 (Improper Privilege Management) vulnerabilities

CVE-2026-31852 — Critical (CVSS 10.0): Jellyfin is an open-source media system. The code-quality.yml GitHub Actions workflow in jellyfin/jellyfin-ios is…
CVE-2025-20282 — Critical (CVSS 10.0): A vulnerability in an internal API of Cisco ISE and Cisco ISE-PIC could allow an unauthenticated, remote attacker to…
CVE-2025-0505 — Critical (CVSS 10.0): On Arista CloudVision systems (virtual or physical on-premise deployments), Zero Touch Provisioning can be used to gain…
CVE-2023-48418 — Critical (CVSS 10.0): In checkDebuggingDisallowed of DeviceVersionFragment.java, there is a possible way to access adb before SUW…
CVE-2023-48419 — Critical (CVSS 10.0): An attacker in the wifi vicinity of a target Google Home can spy on the victim, resulting in Elevation of Privilege
CVE-2023-31273 — Critical (CVSS 10.0): Protection mechanism failure in some Intel DCM software before version 5.2 may allow an unauthenticated user to…

Browse all CWE-269 (Improper Privilege Management) vulnerabilities →