# CVE-2020-3120: Cisco FXOS, IOS XR, and NX-OS Software Cisco Discovery Protocol Denial of Service Vulnerability

> An adjacent attacker can cause a device reload and denial of service by sending malicious Cisco Discovery Protocol packets to affected Cisco network operating systems.

- **Severity:** High 7.4 (`CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H`)
- **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:** 5 Feb 2020
- **Updated:** 15 Nov 2024
- **Also known as:** GHSA-vw86-rxwf-9vhm

## What is CVE-2020-3120?

CVE-2020-3120 is a high-severity denial of service vulnerability in Cisco Firepower Extensible Operating System, published on 5 Feb 2020. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A vulnerability in the Cisco Discovery Protocol implementation for Cisco FXOS Software, Cisco IOS XR Software, and Cisco NX-OS Software could allow an unauthenticated, adjacent attacker to cause a reload of an affected device, resulting in a denial of service (DoS) condition. The vulnerability is due to a missing check when the affected software processes Cisco Discovery Protocol messages. An attacker could exploit this vulnerability by sending a malicious Cisco Discovery Protocol packet to an affected device. A successful exploit could allow the attacker to exhaust system memory, causing the device to reload. Cisco Discovery Protocol is a Layer 2 protocol. To exploit this vulnerability, an attacker must be in the same broadcast domain as the affected device (Layer 2 adjacent).

Weakness: CWE-190 (Integer Overflow or Wraparound)

## Which versions are affected by CVE-2020-3120?

It affects 5 products.


Products: Cisco Firepower Extensible Operating System, Cisco Fxos, Cisco Ios Xr, Cisco Nx-Os, Cisco Ucs Manager.

## How do I fix CVE-2020-3120?

No fix has been published for CVE-2020-3120 yet. Limit exposure of the affected software until one is available.

## Is CVE-2020-3120 being exploited?

There is no known exploitation of CVE-2020-3120 in the wild and no public exploit code.

## Other vulnerabilities in Cisco Firepower Extensible Operating System

- [CVE-2018-0310](https://insights.sbomify.com/CVE-2018-0310/): Information disclosure in Cisco FXOS and NX-OS unknown (critical 9.8)
- [CVE-2015-6435](https://insights.sbomify.com/CVE-2015-6435/): Command injection in n/a (critical 9.8)
- [CVE-2021-1368](https://insights.sbomify.com/CVE-2021-1368/): Memory corruption in Cisco NX-OS Software (high 8.8)
- [CVE-2020-3456](https://insights.sbomify.com/CVE-2020-3456/): Cisco FXOS Software Firepower Chassis Manager Cross-Site Request Forgery Vulnerability (high 8.8)
- [CVE-2020-3172](https://insights.sbomify.com/CVE-2020-3172/): Cisco FXOS and NX-OS Software Cisco Discovery Protocol Arbitrary Code Execution and Denial of Service Vulnerability (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-3120 and fix it if it is affected.

What it is: CVE-2020-3120 is a high-severity denial of service vulnerability in Cisco Firepower Extensible Operating System, published on 5 Feb 2020. 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-2020-3120 in the wild and no public exploit code.

Affected product: Cisco Firepower Extensible Operating System. 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-2020-3120/ (Markdown: https://insights.sbomify.com/CVE-2020-3120/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-3120
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-3120
- OSV: https://osv.dev/vulnerability/CVE-2020-3120

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-3120/
Summaries are generated and may contain mistakes; the official description above is the record.