# CVE-2021-42707: WECON PLC Editor

> An out-of-bounds write in WECON PLC Editor allows attackers to execute arbitrary code via malicious project files.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 22 Nov 2021
- **Updated:** 16 Sep 2024
- **Also known as:** GHSA-83cj-78f4-89p2

## What is CVE-2021-42707?

CVE-2021-42707 is a high-severity memory corruption vulnerability in WECON PLC Editor, published on 22 Nov 2021. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

PLC Editor Versions 1.3.8 and prior is vulnerable to an out-of-bounds write while processing project files, which may allow an attacker to execute arbitrary code.

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2021-42707?

It affects 1 product.


Products: We-Con Plc Editor.

## How do I fix CVE-2021-42707?

No fix has been published for CVE-2021-42707 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-42707 being exploited?

There is no known exploitation of CVE-2021-42707 in the wild and no public exploit code.

## Other vulnerabilities in WECON PLC Editor

- [CVE-2020-25177](https://insights.sbomify.com/CVE-2020-25177/): Memory corruption in WECON PLC Editor (high 8.8)
- [CVE-2020-25181](https://insights.sbomify.com/CVE-2020-25181/): Memory corruption in WECON PLC Editor (high 8.8)
- [CVE-2021-42705](https://insights.sbomify.com/CVE-2021-42705/): WECON PLC Editor (high 7.8)
- [CVE-2019-18236](https://insights.sbomify.com/CVE-2019-18236/): Memory corruption in WECON PLC Editor (high 7.8)
- [CVE-2018-14792](https://insights.sbomify.com/CVE-2018-14792/): Code injection in PLC Editor (medium 6.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-42707 and fix it if it is affected.

What it is: CVE-2021-42707 is a high-severity memory corruption vulnerability in WECON PLC Editor, published on 22 Nov 2021. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2021-42707 in the wild and no public exploit code.

Affected product: WECON PLC Editor. 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-2021-42707/ (Markdown: https://insights.sbomify.com/CVE-2021-42707/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-42707
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-42707
- OSV: https://osv.dev/vulnerability/CVE-2021-42707

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-42707/
Summaries are generated and may contain mistakes; the official description above is the record.