# CVE-2022-4856: Modbus Tools Modbus Slave mbs File mbslave.exe buffer overflow

> A remote buffer overflow in Modbus Slave allows attackers to execute arbitrary code via a malicious mbs file.

- **Severity:** Medium 6.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 30 Dec 2022
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-rxg3-r5j8-3qv5

## What is CVE-2022-4856?

CVE-2022-4856 is a medium-severity memory corruption vulnerability in Modbus Slave, published on 30 Dec 2022. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

A vulnerability has been found in Modbus Tools Modbus Slave up to 7.5.1 and classified as critical. Affected by this vulnerability is an unknown functionality of the file mbslave.exe of the component mbs File Handler. The manipulation leads to buffer overflow. The attack can be launched remotely. The exploit has been disclosed to the public and may be used. The identifier VDB-217021 was assigned to this vulnerability.

Weakness: CWE-120 (Buffer Copy without Checking Size of Input)

## Which versions are affected by CVE-2022-4856?

It affects 1 product.


Products: Modbustools Modbus Slave.

## How do I fix CVE-2022-4856?

No fix has been published for CVE-2022-4856 yet. Limit exposure of the affected software until one is available.

## Is CVE-2022-4856 being exploited?

There is no known exploitation of CVE-2022-4856 in the wild and no public exploit code.

## Other vulnerabilities in Modbus Slave

- [CVE-2018-18759](https://insights.sbomify.com/CVE-2018-18759/): Memory corruption in n/a (high 7.5)
- [CVE-2022-1068](https://insights.sbomify.com/CVE-2022-1068/): Modbus Tools Modbus Slave Stack-Based Buffer Overflow (medium 5.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2022-4856 and fix it if it is affected.

What it is: CVE-2022-4856 is a medium-severity memory corruption vulnerability in Modbus Slave, published on 30 Dec 2022. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2022-4856 in the wild and no public exploit code.

Affected product: Modbus Slave. 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-2022-4856/ (Markdown: https://insights.sbomify.com/CVE-2022-4856/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2022-4856
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2022-4856
- OSV: https://osv.dev/vulnerability/CVE-2022-4856

---
From sbomify Insights: https://insights.sbomify.com/CVE-2022-4856/
Summaries are generated and may contain mistakes; the official description above is the record.