# CVE-2017-6034: Schneider Electric Modicon Modbus Protocol Authentication Bypass by Capture-replay

> Attackers can bypass authentication by replaying cleartext Modbus commands to control PLC operations like run, stop, upload, and download.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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:** 30 Jun 2017
- **Updated:** 4 Jun 2026
- **Also known as:** GHSA-m8hv-35c9-8jrx

## What is CVE-2017-6034?

CVE-2017-6034 is a critical authentication bypass vulnerability in Schneider Electric Modicon Modbus Protocol, published on 30 Jun 2017. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An authentication bypass by capture-replay issue was discovered in Schneider Electric Modicon Modbus Protocol. Sensitive information is transmitted in cleartext in the Modicon Modbus protocol, which may allow an attacker to replay the following commands: run, stop, upload, and download.

Weakness: CWE-287 (Improper Authentication), CWE-294 (Authentication Bypass by Capture-replay)

## Which versions are affected by CVE-2017-6034?

It affects 1 product.


Products: Schneider-Electric Modbus Firmware.

## How do I fix CVE-2017-6034?

No fix has been published for CVE-2017-6034 yet. Limit exposure of the affected software until one is available.

## Is CVE-2017-6034 being exploited?

There is no known exploitation of CVE-2017-6034 in the wild and no public exploit code.

## Other vulnerabilities in Schneider Electric Modicon Modbus Protocol

- [CVE-2017-6032](https://insights.sbomify.com/CVE-2017-6032/): Security feature bypass in Schneider Electric Modicon Modbus Protocol (medium 5.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2017-6034 and fix it if it is affected.

What it is: CVE-2017-6034 is a critical authentication bypass vulnerability in Schneider Electric Modicon Modbus Protocol, published on 30 Jun 2017. 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-2017-6034 in the wild and no public exploit code.

Affected product: Schneider Electric Modicon Modbus Protocol. 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-2017-6034/ (Markdown: https://insights.sbomify.com/CVE-2017-6034/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2017-6034
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2017-6034
- OSV: https://osv.dev/vulnerability/CVE-2017-6034

---
From sbomify Insights: https://insights.sbomify.com/CVE-2017-6034/
Summaries are generated and may contain mistakes; the official description above is the record.