# CVE-2020-3517: Cisco FXOS and NX-OS Software Cisco Fabric Services Denial of Service Vulnerability

> Unauthenticated attackers can cause device reloads and denial of service by sending malicious Cisco Fabric Services messages to affected Cisco NX-OS devices.

- **Severity:** High 8.6 (`CVSS:3.0/AV:N/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:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 27 Aug 2020
- **Updated:** 13 Nov 2024
- **Also known as:** GHSA-8cw5-4pj3-6hp9

## What is CVE-2020-3517?

CVE-2020-3517 is a high-severity vulnerability in Cisco Firepower Extensible Operating System, published on 27 Aug 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability in the Cisco Fabric Services component of Cisco FXOS Software and Cisco NX-OS Software could allow an unauthenticated attacker to cause process crashes, which could result in a denial of service (DoS) condition on an affected device. The attack vector is configuration dependent and could be remote or adjacent. For more information about the attack vector, see the Details section of this advisory. The vulnerability is due to insufficient error handling when the affected software parses Cisco Fabric Services messages. An attacker could exploit this vulnerability by sending malicious Cisco Fabric Services messages to an affected device. A successful exploit could allow the attacker to cause a reload of an affected device, which could result in a DoS condition.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2020-3517?

It affects 2 products.


Products: Cisco Firepower Extensible Operating System, Cisco Nx-Os.

## How do I fix CVE-2020-3517?

No fix has been published for CVE-2020-3517 yet. Limit exposure of the affected software until one is available.

## Is CVE-2020-3517 being exploited?

There is no known exploitation of CVE-2020-3517 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-2020-3517 and fix it if it is affected.

What it is: CVE-2020-3517 is a high-severity vulnerability in Cisco Firepower Extensible Operating System, published on 27 Aug 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2020-3517 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-2020-3517/ (Markdown: https://insights.sbomify.com/CVE-2020-3517/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-3517
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-3517
- OSV: https://osv.dev/vulnerability/CVE-2020-3517

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-3517/
Summaries are generated and may contain mistakes; the official description above is the record.