# CVE-2021-34593: CODESYS V2 runtime: unauthenticated invalid requests may result in denial-of-service

> Unauthenticated attackers can cause denial-of-service conditions in CODESYS V2 Runtime by sending crafted invalid requests, stopping PLC programs or blocking communication.

- **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:** 26 Oct 2021
- **Updated:** 17 Sep 2024
- **Also known as:** GHSA-mp42-p5v3-r5p6

## What is CVE-2021-34593?

CVE-2021-34593 is a high-severity denial of service vulnerability in CODESYS V2, published on 26 Oct 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

In CODESYS V2 Runtime Toolkit 32 Bit full and PLCWinNT prior to versions V2.4.7.56 unauthenticated crafted invalid requests may result in several denial-of-service conditions. Running PLC programs may be stopped, memory may be leaked, or further communication clients may be blocked from accessing the PLC.

Weakness: CWE-755 (Improper Handling of Exceptional Conditions)

## Which versions are affected by CVE-2021-34593?

It affects 15 products.


Products: Codesys Plcwinnt, Codesys Runtime Toolkit, Wago 750-8202 Firmware, Wago 750-8203 Firmware, Wago 750-8204 Firmware, Wago 750-8206 Firmware, Wago 750-8207 Firmware, Wago 750-8208 Firmware, Wago 750-8210 Firmware, Wago 750-8211 Firmware, Wago 750-8212 Firmware, Wago 750-8213 Firmware, Wago 750-8214 Firmware, Wago 750-8216 Firmware, Wago 750-8217 Firmware.

## How do I fix CVE-2021-34593?

No fix has been published for CVE-2021-34593 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-34593 being exploited?

There is no known exploitation of CVE-2021-34593 in the wild and no public exploit code.

## Other vulnerabilities in CODESYS V2

- [CVE-2022-31806](https://insights.sbomify.com/CVE-2022-31806/): Insecure default settings in CODESYS Runtime Toolkit 32 bit full and CODESYS PLCWinNT (critical 9.8)
- [CVE-2022-32137](https://insights.sbomify.com/CVE-2022-32137/): CODESYS Runtime System prone to heap based buffer overflow (high 8.8)
- [CVE-2022-32138](https://insights.sbomify.com/CVE-2022-32138/): CODESYS runtime system prone to denial of service due to Unexpected Sign Extension (high 8.8)
- [CVE-2022-32143](https://insights.sbomify.com/CVE-2022-32143/): CODESYS runtime system prone to directory acces (high 8.8)
- [CVE-2022-1965](https://insights.sbomify.com/CVE-2022-1965/): CODESYS runtime system prone to file deletion due to improper error handling (high 8.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-34593 and fix it if it is affected.

What it is: CVE-2021-34593 is a high-severity denial of service vulnerability in CODESYS V2, published on 26 Oct 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-2021-34593 in the wild and no public exploit code.

Affected product: CODESYS V2. 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-2021-34593/ (Markdown: https://insights.sbomify.com/CVE-2021-34593/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-34593
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-34593
- OSV: https://osv.dev/vulnerability/CVE-2021-34593

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-34593/
Summaries are generated and may contain mistakes; the official description above is the record.