# CVE-2018-4002: Denial of service in CUJO

> Unauthenticated attackers can crash the mdnscap process on CUJO Smart Firewalls by sending malicious mDNS packets that cause stack exhaustion.

- **Severity:** Medium 5.3 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/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:** 31 Oct 2019
- **Updated:** 5 Aug 2024
- **Also known as:** GHSA-q2rr-fhp3-v3j2

## What is CVE-2018-4002?

CVE-2018-4002 is a medium-severity denial of service vulnerability in CUJO, published on 31 Oct 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An exploitable denial-of-service vulnerability exists in the mdnscap binary of the CUJO Smart Firewall running firmware 7003. When parsing labels in mDNS packets, the firewall unsafely handles label compression pointers, leading to an uncontrolled recursion that eventually exhausts the stack, crashing the mdnscap process. An unauthenticated attacker can send an mDNS message to trigger this vulnerability.

Weakness: CWE-674 (Uncontrolled Recursion)

## Which versions are affected by CVE-2018-4002?

It affects 1 product.


Products: Cujo Smart Firewall Firmware.

## How do I fix CVE-2018-4002?

No fix has been published for CVE-2018-4002 yet. Limit exposure of the affected software until one is available.

## Is CVE-2018-4002 being exploited?

There is no known exploitation of CVE-2018-4002 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2018-4002 and fix it if it is affected.

What it is: CVE-2018-4002 is a medium-severity denial of service vulnerability in CUJO, published on 31 Oct 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-2018-4002 in the wild and no public exploit code.

Affected product: CUJO. 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-2018-4002/ (Markdown: https://insights.sbomify.com/CVE-2018-4002/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-4002
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-4002
- OSV: https://osv.dev/vulnerability/CVE-2018-4002

---
From sbomify Insights: https://insights.sbomify.com/CVE-2018-4002/
Summaries are generated and may contain mistakes; the official description above is the record.