# CVE-2018-7789: Denial of service in Modicon M221, all references, all versions prior to firmware V1.6.2.0

> Unauthorized users can remotely reboot Schneider Electric Modicon M221 PLCs via crafted protocol frames, causing service disruption.

- **Severity:** Medium 4.8 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/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:** 29 Aug 2018
- **Updated:** 29 May 2026
- **Also known as:** GHSA-mw2w-h237-7rhw

## What is CVE-2018-7789?

CVE-2018-7789 is a medium-severity denial of service vulnerability in Schneider Electric SE Modicon M221, all references, all versions prior to firmware V1.6.2.0, published on 29 Aug 2018. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An Improper Check for Unusual or Exceptional Conditions vulnerability exists in Schneider Electric's Modicon M221 product (all references, all versions prior to firmware V1.6.2.0). The vulnerability allows unauthorized users to remotely reboot Modicon M221 using crafted programing protocol frames.

Weakness: CWE-754 (Improper Check for Unusual or Exceptional Conditions)

## Which versions are affected by CVE-2018-7789?

It affects 1 product.


Products: Schneider-Electric Modicon M221 Firmware.

## How do I fix CVE-2018-7789?

No fix has been published for CVE-2018-7789 yet. Limit exposure of the affected software until one is available.

## Is CVE-2018-7789 being exploited?

There is no known exploitation of CVE-2018-7789 in the wild and no public exploit code.

## Other vulnerabilities in Schneider Electric SE Modicon M221, all references, all versions prior to firmware V1.6.2.0

- [CVE-2020-28214](https://insights.sbomify.com/CVE-2020-28214/): Weak cryptography in Modicon M221 (all references, all versions) (critical 9.8)
- [CVE-2018-7790](https://insights.sbomify.com/CVE-2018-7790/): Auth bypass in Modicon M221, all references, all versions prior to firmware V1.6.2.0 (critical 9.8)
- [CVE-2018-7791](https://insights.sbomify.com/CVE-2018-7791/): Auth bypass in Modicon M221, all references, all versions prior to firmware V1.6.2.0 (critical 9.8)
- [CVE-2018-7821](https://insights.sbomify.com/CVE-2018-7821/): Denial of service in SoMachine Basic and Modicon M221, SoMachine Basic, all versions Modicon M221, all references, all versions prior to firmware V1.10.0.0 (high 7.5)
- [CVE-2018-7792](https://insights.sbomify.com/CVE-2018-7792/): Weak cryptography in Modicon M221, all references, all versions prior to firmware V1.6.2.0 (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2018-7789 and fix it if it is affected.

What it is: CVE-2018-7789 is a medium-severity denial of service vulnerability in Schneider Electric SE Modicon M221, all references, all versions prior to firmware V1.6.2.0, published on 29 Aug 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-2018-7789 in the wild and no public exploit code.

Affected product: Schneider Electric SE Modicon M221, all references, all versions prior to firmware V1.6.2.0. 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-2018-7789/ (Markdown: https://insights.sbomify.com/CVE-2018-7789/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-7789
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-7789
- OSV: https://osv.dev/vulnerability/CVE-2018-7789

---
From sbomify Insights: https://insights.sbomify.com/CVE-2018-7789/
Summaries are generated and may contain mistakes; the official description above is the record.