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CVE-2021-1388

38
FAUCET Score

CVE-2021-1388 is a critical authentication bypass vulnerability in Cisco ACI Multi-Site Orchestrator (MSO) and managed Application Policy Infrastructure Controller (APIC) devices. It allows an unauthenticated, remote attacker to gain administrator-level privileges due to improper token validation on a specific API endpoint. With a CVSS score of 10.0, this vulnerability presents a severe risk, enabling complete compromise of affected systems. While there is no known active exploitation or public exploit code, the vulnerability has garnered significant community attention with 12 mentions and 2 media articles, indicating high awareness of its potential impact.

Impacted Technologies

VendorProductVersion(s)CPE
>= 3.0, < 3.0\(3m\)CPE matchmatch criteria
cpe:2.3:a:cisco:aci_multi-site_orchestrator:*:*:*:*:*:*:*:*
3.0\(3i\)CPE matchmatch criteria
cpe:2.3:a:cisco:application_policy_infrastructure_controller:3.0\(3i\):*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

10.0CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
CHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
6.0
CvssVersion
3.1

Exploit Intelligence

EPSS Score
14.36%
Probability of exploitation in next 30 days
EPSS Percentile
96.2%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.1436 is in the 92nd percentile among its peer group of 36,862 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Vendor Patches (1)

ciscovendor investigatingvia nvd_reference
View patch

References

tools.cisco.com / security/center/content/CiscoSecurityAdvisory/cisco-sa-mso-authbyp-bb5GmBQv
Vendor Advisory