# CVE-2021-20586: Denial of service in Robot Controller MELFA FR Series; Robot Controller CR Series; Cooperative Robot ASSISTA

> Remote unauthenticated attackers can cause denial of service in Mitsubishi MELFA and ASSISTA robot controllers by flooding them with burst packets.

- **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:** 29 Jan 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-c9mw-29g5-hf3h

## What is CVE-2021-20586?

CVE-2021-20586 is a high-severity denial of service vulnerability in Robot Controller MELFA FR Series; Robot Controller CR Series; Cooperative Robot ASSISTA, published on 29 Jan 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Resource management errors vulnerability in a robot controller of MELFA FR Series(controller "CR800-*V*D" of RV-*FR***-D-* all versions, controller "CR800-*HD" of RH-*FRH***-D-* all versions, controller "CR800-*HRD" of RH-*FRHR***-D-* all versions, controller "CR800-*V*R with R16RTCPU" of RV-*FR***-R-* all versions, controller "CR800-*HR with R16RTCPU" of RH-*FRH***-R-* all versions, controller "CR800-*HRR with R16RTCPU" of RH-*FRHR***-R-* all versions, controller "CR800-*V*Q with Q172DSRCPU" of RV-*FR***-Q-* all versions, controller "CR800-*HQ with Q172DSRCPU" of RH-*FRH***-Q-* all versions, controller "CR800-*HRQ with Q172DSRCPU" of RH-*FRHR***-Q-* all versions) and a robot controller of MELFA CR Series(controller "CR800-CVD" of RV-8CRL-D-* all versions, controller "CR800-CHD" of RH-*CRH**-D-* all versions) as well as a cooperative robot ASSISTA(controller "CR800-05VD" of RV-5AS-D-* all versions) allows a remote unauthenticated attacker to cause a DoS of the execution of the robot program and the Ethernet communication by sending a large amount of packets in burst over a short period of time. As a result of DoS, an error may occur. A reset is required to recover it if the error occurs.

## Which versions are affected by CVE-2021-20586?

It affects 33 products.


Products: Mitsubishielectric Rh12frh55 Firmware, Mitsubishielectric Rh12frh85 Firmware, Mitsubishielectric Rh12rfh70 Firmware, Mitsubishielectric Rh1frhr Firmware, Mitsubishielectric Rh20frh100 Firmware, Mitsubishielectric Rh20frh85 Firmware, Mitsubishielectric Rh3frh35 Firmware, Mitsubishielectric Rh3frh45 Firmware, Mitsubishielectric Rh3frh55 Firmware, Mitsubishielectric Rh3frhr Firmware, Mitsubishielectric Rh6frh35 Firmware, Mitsubishielectric Rh6frh45 Firmware, Mitsubishielectric Rh6frh55 Firmware, Mitsubishielectric Rv13fr Firmware, Mitsubishielectric Rv13frl Firmware, Mitsubishielectric Rv13frlm\/C Firmware, Mitsubishielectric Rv13frm\/C Firmware, Mitsubishielectric Rv20fr Firmware, Mitsubishielectric Rv20frm\/C Firmware, Mitsubishielectric Rv2fr\(b\) Firmware and 13 more.

## How do I fix CVE-2021-20586?

No fix has been published for CVE-2021-20586 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-20586 being exploited?

There is no known exploitation of CVE-2021-20586 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-20586 and fix it if it is affected.

What it is: CVE-2021-20586 is a high-severity denial of service vulnerability in Robot Controller MELFA FR Series; Robot Controller CR Series; Cooperative Robot ASSISTA, published on 29 Jan 2021. 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-2021-20586 in the wild and no public exploit code.

Affected product: Robot Controller MELFA FR Series; Robot Controller CR Series; Cooperative Robot ASSISTA. 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-2021-20586/ (Markdown: https://insights.sbomify.com/CVE-2021-20586/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-20586
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-20586
- OSV: https://osv.dev/vulnerability/CVE-2021-20586

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From sbomify Insights: https://insights.sbomify.com/CVE-2021-20586/
Summaries are generated and may contain mistakes; the official description above is the record.