# CVE-2021-1229: Cisco NX-OS Software ICMP Version 6 Memory Leak Denial of Service Vulnerability

> Remote attackers can cause a memory leak in Cisco NX-OS via crafted ICMPv6 packets, leading to denial of service.

- **Severity:** Medium 5.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 24 Feb 2021
- **Updated:** 8 Nov 2024
- **Also known as:** GHSA-pqr7-274x-7pxj

## What is CVE-2021-1229?

CVE-2021-1229 is a medium-severity denial of service vulnerability in Cisco Nx-Os, published on 24 Feb 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability in ICMP Version 6 (ICMPv6) processing in Cisco NX-OS Software could allow an unauthenticated, remote attacker to cause a slow system memory leak, which over time could lead to a denial of service (DoS) condition. This vulnerability is due to improper error handling when an IPv6-configured interface receives a specific type of ICMPv6 packet. An attacker could exploit this vulnerability by sending a sustained rate of crafted ICMPv6 packets to a local IPv6 address on a targeted device. A successful exploit could allow the attacker to cause a system memory leak in the ICMPv6 process on the device. As a result, the ICMPv6 process could run out of system memory and stop processing traffic. The device could then drop all ICMPv6 packets, causing traffic instability on the device. Restoring device functionality would require a device reboot.

Weakness: CWE-401 (Missing Release of Memory after Effective Lifetime)

## Which versions are affected by CVE-2021-1229?

It affects 1 product.


Products: Cisco Nx-Os.

## How do I fix CVE-2021-1229?

No fix has been published for CVE-2021-1229 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-1229 being exploited?

There is no known exploitation of CVE-2021-1229 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-2021-1229 and fix it if it is affected.

What it is: CVE-2021-1229 is a medium-severity denial of service vulnerability in Cisco Nx-Os, published on 24 Feb 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-2021-1229 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-2021-1229/ (Markdown: https://insights.sbomify.com/CVE-2021-1229/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-1229
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-1229
- OSV: https://osv.dev/vulnerability/CVE-2021-1229

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-1229/
Summaries are generated and may contain mistakes; the official description above is the record.