# CVE-2021-1586: Cisco Nexus 9000 Series Fabric Switches ACI Mode Multi-Pod and Multi-Site TCP Denial of Service Vulnerability

> Unauthenticated remote attackers can cause unexpected device restarts via crafted TCP traffic in Multi-Pod or Multi-Site ACI configurations.

- **Severity:** High 8.6 (`CVSS:3.1/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:** 25 Aug 2021
- **Updated:** 7 Nov 2024
- **Also known as:** GHSA-cvmj-92cp-78jp

## What is CVE-2021-1586?

CVE-2021-1586 is a high-severity denial of service vulnerability in Cisco Nx-Os, published on 25 Aug 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability in the Multi-Pod or Multi-Site network configurations for Cisco Nexus 9000 Series Fabric Switches in Application Centric Infrastructure (ACI) mode could allow an unauthenticated, remote attacker to unexpectedly restart the device, resulting in a denial of service (DoS) condition. This vulnerability exists because TCP traffic sent to a specific port on an affected device is not properly sanitized. An attacker could exploit this vulnerability by sending crafted TCP data to a specific port that is listening on a public-facing IP address for the Multi-Pod or Multi-Site configuration. A successful exploit could allow the attacker to cause the device to restart unexpectedly, resulting in a DoS condition.

Weakness: CWE-345 (Insufficient Verification of Data Authenticity)

## Which versions are affected by CVE-2021-1586?

It affects 1 product.


Products: Cisco Nx-Os.

## How do I fix CVE-2021-1586?

No fix has been published for CVE-2021-1586 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-1586 being exploited?

There is no known exploitation of CVE-2021-1586 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-2021-1586 and fix it if it is affected.

What it is: CVE-2021-1586 is a high-severity denial of service vulnerability in Cisco Nx-Os, published on 25 Aug 2021. 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-2021-1586 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-2021-1586/ (Markdown: https://insights.sbomify.com/CVE-2021-1586/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-1586
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-1586
- OSV: https://osv.dev/vulnerability/CVE-2021-1586

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-1586/
Summaries are generated and may contain mistakes; the official description above is the record.