# CVE-2019-1751: Cisco IOS Software NAT64 Denial of Service Vulnerability

> Remote unauthenticated attackers can cause a denial of service by sending specific IPv4 packets to devices running Cisco IOS with NAT64 enabled.

- **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:** 28 Mar 2019
- **Updated:** 19 Nov 2024
- **Also known as:** GHSA-cgx8-9m8p-2q4p

## What is CVE-2019-1751?

CVE-2019-1751 is a high-severity denial of service vulnerability in Cisco Ios, published on 28 Mar 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability in the Network Address Translation 64 (NAT64) functions of Cisco IOS Software could allow an unauthenticated, remote attacker to cause either an interface queue wedge or a device reload. The vulnerability is due to the incorrect handling of certain IPv4 packet streams that are sent through the device. An attacker could exploit this vulnerability by sending specific IPv4 packet streams through the device. An exploit could allow the attacker to either cause an interface queue wedge or a device reload, resulting in a denial of service (DoS) condition.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2019-1751?

It affects 1 product.


Products: Cisco Ios.

## How do I fix CVE-2019-1751?

No fix has been published for CVE-2019-1751 yet. Limit exposure of the affected software until one is available.

## Is CVE-2019-1751 being exploited?

There is no known exploitation of CVE-2019-1751 in the wild and no public exploit code.

## Other vulnerabilities in Cisco Ios

- [CVE-2017-12240](https://insights.sbomify.com/CVE-2017-12240/): Cisco IOS and IOS XE Software DHCP Remote Code Execution (critical 9.8, exploited in the wild)
- [CVE-2017-3881](https://insights.sbomify.com/CVE-2017-3881/): Cisco IOS and IOS XE Remote Code Execution (critical 9.8, exploited in the wild)
- [CVE-2018-0167](https://insights.sbomify.com/CVE-2018-0167/): Cisco IOS, XR, and XE Software Buffer Overflow (high 8.8, exploited in the wild)
- [CVE-2017-6736](https://insights.sbomify.com/CVE-2017-6736/): Cisco IOS and IOS XE Software SNMP Remote Code Execution (high 8.8, exploited in the wild)
- [CVE-2017-6737](https://insights.sbomify.com/CVE-2017-6737/): Cisco IOS and IOS XE Software SNMP Remote Code Execution (high 8.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2019-1751 and fix it if it is affected.

What it is: CVE-2019-1751 is a high-severity denial of service vulnerability in Cisco Ios, published on 28 Mar 2019. 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-2019-1751 in the wild and no public exploit code.

Affected product: Cisco Ios. 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-2019-1751/ (Markdown: https://insights.sbomify.com/CVE-2019-1751/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2019-1751
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2019-1751
- OSV: https://osv.dev/vulnerability/CVE-2019-1751

---
From sbomify Insights: https://insights.sbomify.com/CVE-2019-1751/
Summaries are generated and may contain mistakes; the official description above is the record.