# CVE-2018-20818: Memory corruption in n/a

> A buffer overflow in OpenPLC's modbus handler can crash the PLC, impacting industrial control system availability.

- **Severity:** Critical 9.8 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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:** 21 Apr 2019
- **Updated:** 5 Aug 2024
- **Also known as:** GHSA-j22f-7hvx-mqp8

## What is CVE-2018-20818?

CVE-2018-20818 is a critical memory corruption vulnerability in n/a, published on 21 Apr 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A buffer overflow vulnerability was discovered in the OpenPLC controller, in the OpenPLC_v2 and OpenPLC_v3 versions. It occurs in the modbus.cpp mapUnusedIO() function, which can cause a runtime crash of the PLC or possibly have unspecified other impact.

Weakness: CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer)

## Which versions are affected by CVE-2018-20818?

It affects 2 products.


Products: Openplcproject Openplc V2 Firmware, Openplcproject Openplc V3 Firmware.

## How do I fix CVE-2018-20818?

No fix has been published for CVE-2018-20818 yet. Limit exposure of the affected software until one is available.

## Is CVE-2018-20818 being exploited?

There is no known exploitation of CVE-2018-20818 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2018-20818 and fix it if it is affected.

What it is: CVE-2018-20818 is a critical memory corruption vulnerability in n/a, published on 21 Apr 2019. 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-2018-20818 in the wild and no public exploit code.

Affected product: n/a. 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-2018-20818/ (Markdown: https://insights.sbomify.com/CVE-2018-20818/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-20818
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-20818
- OSV: https://osv.dev/vulnerability/CVE-2018-20818

---
From sbomify Insights: https://insights.sbomify.com/CVE-2018-20818/
Summaries are generated and may contain mistakes; the official description above is the record.