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

> Attackers can cause denial of service on Phoenix Contact PLCnext Control devices by sending specially crafted JSON requests.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 27 Sep 2021
- **Updated:** 16 Sep 2024
- **Also known as:** GHSA-5jgp-38vj-293v

## What is CVE-2021-34570?

CVE-2021-34570 is a high-severity denial of service vulnerability in Phoenix Contact AXC F, published on 27 Sep 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2021-34570?

It affects 6 products.


Products: Phoenixcontact Axc F 1152 Firmware, Phoenixcontact Axc F 2152 Firmware, Phoenixcontact Axc F 2152 Starterkit Firmware, Phoenixcontact Axc F 3152 Firmware, Phoenixcontact Plcnext Technology Starterkit Firmware, Phoenixcontact Rfc 4072s Firmware.

## How do I fix CVE-2021-34570?

No fix has been published for CVE-2021-34570 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-34570 being exploited?

There is no known exploitation of CVE-2021-34570 in the wild and no public exploit code.

## Other vulnerabilities in Phoenix Contact AXC F

- [CVE-2023-46142](https://insights.sbomify.com/CVE-2023-46142/): PHOENIX CONTACT: Insufficient Read and Write Protection to Logic and Runtime Data in PLCnext Control (high 8.8)
- [CVE-2023-46144](https://insights.sbomify.com/CVE-2023-46144/): PHOENIX CONTACT: PLCnext Control prone to download of code without integrity check (medium 6.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-34570 and fix it if it is affected.

What it is: CVE-2021-34570 is a high-severity denial of service vulnerability in Phoenix Contact AXC F, published on 27 Sep 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-34570 in the wild and no public exploit code.

Affected product: Phoenix Contact AXC F. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2021-34570/ (Markdown: https://insights.sbomify.com/CVE-2021-34570/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-34570
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-34570
- OSV: https://osv.dev/vulnerability/CVE-2021-34570

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-34570/
Summaries are generated and may contain mistakes; the official description above is the record.