# CVE-2019-6829: Denial of service in Modicon M340

> Attackers can cause denial of service in Schneider Modicon PLCs by writing to specific memory addresses via Modbus.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/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:** 17 Sep 2019
- **Updated:** 29 May 2026
- **Also known as:** GHSA-25r4-295r-fvqm

## What is CVE-2019-6829?

CVE-2019-6829 is a high-severity denial of service vulnerability in Schneider Electric SE Modicon M340, published on 17 Sep 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A CWE-248: Uncaught Exception vulnerability exists in Modicon M580 (firmware version prior to V2.90) and Modicon M340 (firmware version prior to V3.10), which could cause a possible denial of service when writing to specific memory addresses in the controller over Modbus.

Weakness: CWE-755 (Improper Handling of Exceptional Conditions), CWE-248 (Uncaught Exception)

## Which versions are affected by CVE-2019-6829?

It affects 2 products.


Products: Schneider-Electric Modicon M340 Firmware, Schneider-Electric Modicon M580 Firmware.

## How do I fix CVE-2019-6829?

No fix has been published for CVE-2019-6829 yet. Limit exposure of the affected software until one is available.

## Is CVE-2019-6829 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2019-6829 exists.

## Other vulnerabilities in Schneider Electric SE Modicon M340

- [CVE-2018-7842](https://insights.sbomify.com/CVE-2018-7842/): Auth bypass in Modicon M580 Modicon M340 Modicon Quantum Modicon Premium (critical 9.8)
- [CVE-2018-7846](https://insights.sbomify.com/CVE-2018-7846/): Auth bypass in Modicon M580 Modicon M340 Modicon Quantum Modicon Premium (critical 9.8)
- [CVE-2018-7847](https://insights.sbomify.com/CVE-2018-7847/): Missing authorization in Modicon M580 Modicon M340 Modicon Quantum Modicon Premium (critical 9.8)
- [CVE-2019-6808](https://insights.sbomify.com/CVE-2019-6808/): Missing authorization in Modicon M580 Modicon M340 Modicon Quantum Modicon Premium (critical 9.8)
- [CVE-2019-6845](https://insights.sbomify.com/CVE-2019-6845/): Information disclosure in Modicon M580, Modicon M340, Modicon Premium , Modicon Quantum (all firmware versions) (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2019-6829 and fix it if it is affected.

What it is: CVE-2019-6829 is a high-severity denial of service vulnerability in Schneider Electric SE Modicon M340, published on 17 Sep 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2019-6829 exists.

Affected product: Schneider Electric SE Modicon M340. 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-2019-6829/ (Markdown: https://insights.sbomify.com/CVE-2019-6829/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2019-6829
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2019-6829
- OSV: https://osv.dev/vulnerability/CVE-2019-6829

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From sbomify Insights: https://insights.sbomify.com/CVE-2019-6829/
Summaries are generated and may contain mistakes; the official description above is the record.