# CVE-2018-0476: Cisco IOS XE Software NAT Session Initiation Protocol Application Layer Gateway Denial of Service Vulnerability

> Remote attackers can cause Cisco IOS XE devices to reload by sending crafted SIP packets, resulting in a denial of service.

- **Severity:** Medium 5.9 (`CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/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:** 5 Oct 2018
- **Updated:** 26 Nov 2024
- **Also known as:** GHSA-72m2-hw7c-6c7r

## What is CVE-2018-0476?

CVE-2018-0476 is a medium-severity denial of service vulnerability in Cisco Ios Xe, published on 5 Oct 2018. 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 (NAT) Session Initiation Protocol (SIP) Application Layer Gateway (ALG) of Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause an affected device to reload. The vulnerability is due to improper processing of SIP packets in transit while NAT is performed on an affected device. An unauthenticated, remote attacker could exploit this vulnerability by sending crafted SIP packets via UDP port 5060 through an affected device that is performing NAT for SIP packets. A successful exploit could allow an attacker to cause the device to reload, resulting in a denial of service (DoS) condition.

Weakness: CWE-399

## Which versions are affected by CVE-2018-0476?

It affects 1 product.


Products: Cisco Ios Xe.

## How do I fix CVE-2018-0476?

No fix has been published for CVE-2018-0476 yet. Limit exposure of the affected software until one is available.

## Is CVE-2018-0476 being exploited?

There is no known exploitation of CVE-2018-0476 in the wild and no public exploit code.

## Other vulnerabilities in Cisco Ios Xe

- [CVE-2023-20198](https://insights.sbomify.com/CVE-2023-20198/): Cisco IOS XE Web UI Privilege Escalation (critical 10.0, exploited in the wild)
- [CVE-2018-0151](https://insights.sbomify.com/CVE-2018-0151/): Cisco IOS Software and Cisco IOS XE Software Quality of Service Remote Code Execution (critical 9.8, exploited in the wild)
- [CVE-2023-20273](https://insights.sbomify.com/CVE-2023-20273/): Cisco IOS XE Web UI Command Injection (high 7.2, exploited in the wild)
- [CVE-2025-20188](https://insights.sbomify.com/CVE-2025-20188/): Hardcoded credentials in Cisco IOS XE Software (critical 10.0)
- [CVE-2021-34770](https://insights.sbomify.com/CVE-2021-34770/): Cisco IOS XE Software for Catalyst 9000 Family Wireless Controllers CAPWAP Remote Code Execution Vulnerability (critical 10.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2018-0476 and fix it if it is affected.

What it is: CVE-2018-0476 is a medium-severity denial of service vulnerability in Cisco Ios Xe, published on 5 Oct 2018. 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-2018-0476 in the wild and no public exploit code.

Affected product: Cisco Ios Xe. 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-2018-0476/ (Markdown: https://insights.sbomify.com/CVE-2018-0476/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-0476
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-0476
- OSV: https://osv.dev/vulnerability/CVE-2018-0476

---
From sbomify Insights: https://insights.sbomify.com/CVE-2018-0476/
Summaries are generated and may contain mistakes; the official description above is the record.