# CVE-2020-5543: Other in Mitsubishi Electric MELQIC IU1 series

> Remote attackers can execute malware or disrupt network functions in Mitsubishi Electric MELQIC IU1 series PLCs via crafted packets.

- **Severity:** Critical 9.8 (`CVSS:3.1/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:** 16 Mar 2020
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-q999-969v-8wx8

## What is CVE-2020-5543?

CVE-2020-5543 is a critical vulnerability in Mitsubishi Electric MELQIC IU1 series, published on 16 Mar 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

TCP function included in the firmware of Mitsubishi Electric MELQIC IU1 series IU1-1M20-D firmware version 1.0.7 and earlier does not properly manage sessions, which allows remote attackers to stop the network functions or execute malware via a specially crafted packet.

Weakness: CWE-384 (Session Fixation)

## Which versions are affected by CVE-2020-5543?

It affects 1 product.


Products: Mitsubishielectric Iu1-1m20-D Firmware.

## How do I fix CVE-2020-5543?

No fix has been published for CVE-2020-5543 yet. Limit exposure of the affected software until one is available.

## Is CVE-2020-5543 being exploited?

There is no known exploitation of CVE-2020-5543 in the wild and no public exploit code.

## Other vulnerabilities in Mitsubishi Electric MELQIC IU1 series

- [CVE-2020-5542](https://insights.sbomify.com/CVE-2020-5542/): Memory corruption in Mitsubishi Electric MELQIC IU1 series (critical 9.8)
- [CVE-2020-5544](https://insights.sbomify.com/CVE-2020-5544/): Null dereference in Mitsubishi Electric MELQIC IU1 series (critical 9.8)
- [CVE-2020-5545](https://insights.sbomify.com/CVE-2020-5545/): Auth bypass in Mitsubishi Electric MELQIC IU1 series (critical 9.8)
- [CVE-2020-5547](https://insights.sbomify.com/CVE-2020-5547/): Denial of service in Mitsubishi Electric MELQIC IU1 series (critical 9.8)
- [CVE-2020-5546](https://insights.sbomify.com/CVE-2020-5546/): Command injection in Mitsubishi Electric MELQIC IU1 series (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-5543 and fix it if it is affected.

What it is: CVE-2020-5543 is a critical vulnerability in Mitsubishi Electric MELQIC IU1 series, published on 16 Mar 2020. 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-2020-5543 in the wild and no public exploit code.

Affected product: Mitsubishi Electric MELQIC IU1 series. 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-2020-5543/ (Markdown: https://insights.sbomify.com/CVE-2020-5543/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-5543
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-5543
- OSV: https://osv.dev/vulnerability/CVE-2020-5543

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From sbomify Insights: https://insights.sbomify.com/CVE-2020-5543/
Summaries are generated and may contain mistakes; the official description above is the record.