# CVE-2021-1228: Cisco Nexus 9000 Series Fabric Switches ACI Mode Fabric Infrastructure VLAN Unauthorized Access Vulnerability

> An adjacent attacker can bypass security checks to connect an unauthorized server to the privileged infrastructure VLAN, gaining access to APIC services.

- **Severity:** High 7.4 (`CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 24 Feb 2021
- **Updated:** 8 Nov 2024
- **Also known as:** GHSA-mjqq-xhvr-c2mf

## What is CVE-2021-1228?

CVE-2021-1228 is a high-severity authentication bypass vulnerability in Cisco Nx-Os, published on 24 Feb 2021. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

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.

Weakness: CWE-284 (Improper Access Control)

## Which versions are affected by CVE-2021-1228?

It affects 1 product.


Products: Cisco Nx-Os.

## How do I fix CVE-2021-1228?

No fix has been published for CVE-2021-1228 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-1228 being exploited?

There is no known exploitation of CVE-2021-1228 in the wild and no public exploit code.

## Other vulnerabilities in Cisco Nx-Os

- [CVE-2024-20399](https://insights.sbomify.com/CVE-2024-20399/): Cisco NX-OS Command Injection (medium 6.0, exploited in the wild)
- [CVE-2021-1361](https://insights.sbomify.com/CVE-2021-1361/): Cisco NX-OS Software Unauthenticated Arbitrary File Actions Vulnerability (critical 9.8)
- [CVE-2018-0301](https://insights.sbomify.com/CVE-2018-0301/): Memory corruption in Cisco NX-OS unknown (critical 9.8)
- [CVE-2016-1453](https://insights.sbomify.com/CVE-2016-1453/): Memory corruption in n/a (critical 9.8)
- [CVE-2016-1341](https://insights.sbomify.com/CVE-2016-1341/): Hardcoded credentials in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-1228 and fix it if it is affected.

What it is: CVE-2021-1228 is a high-severity authentication bypass vulnerability in Cisco Nx-Os, published on 24 Feb 2021. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-1228 in the wild and no public exploit code.

Affected product: Cisco Nx-Os. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2021-1228/ (Markdown: https://insights.sbomify.com/CVE-2021-1228/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-1228
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-1228
- OSV: https://osv.dev/vulnerability/CVE-2021-1228

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-1228/
Summaries are generated and may contain mistakes; the official description above is the record.