CVE-2021-1228

What it is

A vulnerability in the fabric infrastructure VLAN connection establishment of Cisco Nexus 9000 Series Fabric Switches in Application Centric Infrastructure (ACI) Mode could allow an unauthenticated, adjacent attacker to bypass security validations and connect an unauthorized server to the infrastructure VLAN. This vulnerability is due to insufficient security requirements during the Link Layer Discovery Protocol (LLDP) setup phase of the infrastructure VLAN. An attacker could exploit this vulnerability by sending a crafted LLDP packet on the adjacent subnet to an affected device. A successful exploit could allow the attacker to connect an unauthorized server to the infrastructure VLAN, which is highly privileged. With a connection to the infrastructure VLAN, the attacker can make unauthorized connections to Cisco Application Policy Infrastructure Controller (APIC) services or join other host endpoints.

At a glance

Exploitability

Can be exploited from the same network segment without logging in. High risk of data tampering.

Exploit odds

0.4% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2021-02-24 20:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 03:31 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.4% in the next 30 days (EPSS).
• Severity: 7.4 HIGH (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2021-02-24 20:15 UTC

Last modified

2026-06-17 03:31 UTC

Exploit probability

0.4% · EPSS, next 30 days

Weakness

CWE-284 · Improper access control

Record status

Modified

Affected

• Cisco nx-os 11.0\(1b\)
• Cisco nx-os 11.0\(1c\)
• Cisco nx-os 11.0\(1d\)
• Cisco nx-os 11.0\(1e\)
• Cisco nx-os 11.0\(2j\)
• Cisco nx-os 11.0\(2m\)
• Cisco nx-os 11.0\(3f\)
• Cisco nx-os 11.0\(3i\)

Attack profile CVSS 3.1 · 7.4

Attack vector

Adjacent network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Changed

Confidentiality

None

Integrity

High

Availability

None

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2021-1228.md and follow it. Check whether this project is affected by CVE-2021-1228. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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