# CVE-2026-3869: Auth bypass in Modicon M580

> Incorrect authentication implementation allows attackers to compromise confidentiality, integrity, and availability of Modicon PLCs when running lower-level applications.

- **Severity:** Critical 9.2 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 11 Sep 2026
- **Updated:** 11 Sep 2026
- **Also known as:** GHSA-g6jw-g6wr-2qcc

## What is CVE-2026-3869?

CVE-2026-3869 is a critical authentication bypass vulnerability in Schneider Electric Modicon M580, published on 11 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

CWE-303 : Incorrect Implementation of Authentication Algorithm vulnerability exists that could cause loss of confidentiality, integrity and availability of the PLC provided an application project with a lower application level is running on the PLC.

Weakness: CWE-303 (Incorrect Implementation of Authentication Algorithm)

## Which versions are affected by CVE-2026-3869?


## How do I fix CVE-2026-3869?

No fix has been published for CVE-2026-3869 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-3869 being exploited?

There is no known exploitation of CVE-2026-3869 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-3869 and fix it if it is affected.

What it is: CVE-2026-3869 is a critical authentication bypass vulnerability in Schneider Electric Modicon M580, published on 11 Sep 2026. 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-2026-3869 in the wild and no public exploit code.

Affected product: Schneider Electric Modicon M580. 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-2026-3869/ (Markdown: https://insights.sbomify.com/CVE-2026-3869/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-3869
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-3869
- OSV: https://osv.dev/vulnerability/CVE-2026-3869

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-3869/
Summaries are generated and may contain mistakes; the official description above is the record.