# CVE-2021-1588: Cisco NX-OS Software MPLS OAM Denial of Service Vulnerability

> Remote attackers can crash MPLS OAM processes on Cisco NX-OS devices by sending malicious packets, causing device reloads and denial of service.

- **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-427g-prh3-hw73

## What is CVE-2021-1588?

CVE-2021-1588 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 MPLS Operation, Administration, and Maintenance (OAM) feature of Cisco NX-OS Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to improper input validation when an affected device is processing an MPLS echo-request or echo-reply packet. An attacker could exploit this vulnerability by sending malicious MPLS echo-request or echo-reply packets to an interface that is enabled for MPLS forwarding on the affected device. A successful exploit could allow the attacker to cause the MPLS OAM process to crash and restart multiple times, causing the affected device to reload and resulting in a DoS condition.

Weakness: CWE-20 (Improper Input Validation), CWE-125 (Out-of-bounds Read), CWE-126 (Buffer Over-read)

## Which versions are affected by CVE-2021-1588?

It affects 1 product.


Products: Cisco Nx-Os.

## How do I fix CVE-2021-1588?

No fix has been published for CVE-2021-1588 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-1588 being exploited?

There is no known exploitation of CVE-2021-1588 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-2021-1588 and fix it if it is affected.

What it is: CVE-2021-1588 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-2021-1588 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-2021-1588/ (Markdown: https://insights.sbomify.com/CVE-2021-1588/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-1588
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-1588
- OSV: https://osv.dev/vulnerability/CVE-2021-1588

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-1588/
Summaries are generated and may contain mistakes; the official description above is the record.