# CVE-2020-5666: Denial of service in MELSEC iQ-R Series CPU Modules

> Remote attackers can cause denial of service in Mitsubishi MELSEC iQ-R CPU modules via crafted HTTP packets, disrupting industrial control operations.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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 Nov 2020
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-5527-cm29-m2f3

## What is CVE-2020-5666?

CVE-2020-5666 is a high-severity denial of service vulnerability in Mitsubishi Electric Corporation MELSEC iQ-R Series CPU Modules, published on 16 Nov 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Uncontrolled resource consumption vulnerability in MELSEC iQ-R Series CPU Modules (R00/01/02CPU Firmware versions from '05' to '19' and R04/08/16/32/120(EN)CPU Firmware versions from '35' to '51') allows a remote attacker to cause an error in a CPU unit via a specially crafted HTTP packet, which may lead to a denial-of-service (DoS) condition in execution of the program and its communication.

Weakness: CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2020-5666?

It affects 8 products.


Products: Mitsubishielectric Melsec Iq-R00 Firmware, Mitsubishielectric Melsec Iq-R01 Firmware, Mitsubishielectric Melsec Iq-R02 Firmware, Mitsubishielectric Melsec Iq-R04 Firmware, Mitsubishielectric Melsec Iq-R08 Firmware, Mitsubishielectric Melsec Iq-R120 Firmware, Mitsubishielectric Melsec Iq-R16 Firmware, Mitsubishielectric Melsec Iq-R32 Firmware.

## How do I fix CVE-2020-5666?

No fix has been published for CVE-2020-5666 yet. Limit exposure of the affected software until one is available.

## Is CVE-2020-5666 being exploited?

There is no known exploitation of CVE-2020-5666 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-5666 and fix it if it is affected.

What it is: CVE-2020-5666 is a high-severity denial of service vulnerability in Mitsubishi Electric Corporation MELSEC iQ-R Series CPU Modules, published on 16 Nov 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-2020-5666 in the wild and no public exploit code.

Affected product: Mitsubishi Electric Corporation MELSEC iQ-R Series CPU Modules. 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-2020-5666/ (Markdown: https://insights.sbomify.com/CVE-2020-5666/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-5666
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-5666
- OSV: https://osv.dev/vulnerability/CVE-2020-5666

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From sbomify Insights: https://insights.sbomify.com/CVE-2020-5666/
Summaries are generated and may contain mistakes; the official description above is the record.