# CVE-2021-43083: Apache PLC4X 0.9.0 Buffer overflow in PLC4C via crafted server response

> An attacker can trigger an integer underflow in the C implementation by sending a malicious response, potentially causing code execution or denial of service.

- **Severity:** High 8.8 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 19 Dec 2021
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-f935-qq4f-pj9f

## What is CVE-2021-43083?

CVE-2021-43083 is a high-severity vulnerability in Apache PLC4X, published on 19 Dec 2021. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Apache PLC4X - PLC4C (Only the C language implementation was effected) was vulnerable to an unsigned integer underflow flaw inside the tcp transport. Users should update to 0.9.1, which addresses this issue. However, in order to exploit this vulnerability, a user would have to actively connect to a mallicious device which could send a response with invalid content. Currently we consider the probability of this being exploited as quite minimal, however this could change in the future, especially with the industrial networks growing more and more together.

Weakness: CWE-191 (Integer Underflow (Wrap or Wraparound)), CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer)

## Which versions are affected by CVE-2021-43083?

It affects 1 product.


Products: Apache Plc4x.

## How do I fix CVE-2021-43083?

No fix has been published for CVE-2021-43083 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-43083 being exploited?

There is no known exploitation of CVE-2021-43083 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-43083 and fix it if it is affected.

What it is: CVE-2021-43083 is a high-severity vulnerability in Apache PLC4X, published on 19 Dec 2021. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-43083 in the wild and no public exploit code.

Affected product: Apache PLC4X. 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-2021-43083/ (Markdown: https://insights.sbomify.com/CVE-2021-43083/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-43083
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-43083
- OSV: https://osv.dev/vulnerability/CVE-2021-43083

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-43083/
Summaries are generated and may contain mistakes; the official description above is the record.