# CVE-2021-20611: Denial of service in MELIPC Series MI5122-VW

> Remote unauthenticated attackers can cause a denial-of-service condition on Mitsubishi PLCs by sending specially crafted packets, requiring a system reset to recover.

- **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:** 1 Dec 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-pmj6-jq7v-c2r6

## What is CVE-2021-20611?

CVE-2021-20611 is a high-severity denial of service vulnerability in Mitsubishi Electric Corporation MELIPC Series MI5122-VW, published on 1 Dec 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Improper Input Validation vulnerability in Mitsubishi Electric MELSEC iQ-R Series R00/01/02CPU, MELSEC iQ-R Series R04/08/16/32/120(EN)CPU, MELSEC iQ-R Series R08/16/32/120SFCPU, MELSEC iQ-R Series R08/16/32/120PCPU, MELSEC iQ-R Series R08/16/32/120PSFCPU, MELSEC iQ-R Series R16/32/64MTCPU, MELSEC iQ-R Series R12CCPU-V, MELSEC Q Series Q03UDECPU, MELSEC Q Series Q04/06/10/13/20/26/50/100UDEHCPU, MELSEC Q Series Q03/04/06/13/26UDVCPU, MELSEC Q Series Q04/06/13/26UDPVCPU, MELSEC Q Series Q12DCCPU-V, MELSEC Q Series Q24DHCCPU-V(G), MELSEC Q Series Q24/26DHCCPU-LS, MELSEC Q Series MR-MQ100, MELSEC Q Series Q172/173DCPU-S1, MELSEC Q Series Q172/173DSCPU, MELSEC Q Series Q170MCPU, MELSEC Q Series Q170MSCPU(-S1), MELSEC L Series L02/06/26CPU(-P), MELSEC L Series L26CPU-(P)BT and MELIPC Series MI5122-VW allows a remote unauthenticated attacker to cause a denial-of-service (DoS) condition by sending specially crafted packets. System reset is required for recovery.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2021-20611?

It affects 55 products.


Products: Mitsubishi Melipc Mi5122-Vw Firmware, Mitsubishi Melsec Iq-R R00 Cpu Firmware, Mitsubishi Melsec Iq-R R01 Cpu Firmware, Mitsubishi Melsec Iq-R R02 Cpu Firmware, Mitsubishi Melsec Iq-R R04 Cpu Firmware, Mitsubishi Melsec Iq-R R04 Pcpu Firmware, Mitsubishi Melsec Iq-R R08 Cpu Firmware, Mitsubishi Melsec Iq-R R08 Pcpu Firmware, Mitsubishi Melsec Iq-R R08 Sfcpu Firmware, Mitsubishi Melsec Iq-R R120 Cpu Firmware, Mitsubishi Melsec Iq-R R120 Pcpu Firmware, Mitsubishi Melsec Iq-R R120 Sfcpu Firmware, Mitsubishi Melsec Iq-R R12 Ccpu-v Firmware, Mitsubishi Melsec Iq-R R16 Cpu Firmware, Mitsubishi Melsec Iq-R R16 Mtcpu Firmware, Mitsubishi Melsec Iq-R R16 Pcpu Firmware, Mitsubishi Melsec Iq-R R16 Sfcpu Firmware, Mitsubishi Melsec Iq-R R32 Cpu Firmware, Mitsubishi Melsec Iq-R R32 Mtcpu Firmware, Mitsubishi Melsec Iq-R R32 Pcpu Firmware and 35 more.

## How do I fix CVE-2021-20611?

No fix has been published for CVE-2021-20611 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-20611 being exploited?

There is no known exploitation of CVE-2021-20611 in the wild and no public exploit code.

## Other vulnerabilities in Mitsubishi Electric Corporation MELIPC Series MI5122-VW

- [CVE-2022-33324](https://insights.sbomify.com/CVE-2022-33324/): Denial-of-Service Vulnerability in Ethernet port of MELSEC iQ-R, iQ-L Series and MELIPC Series (high 7.5)
- [CVE-2021-20609](https://insights.sbomify.com/CVE-2021-20609/): Denial of service in MELIPC Series MI5122-VW (high 7.5)
- [CVE-2021-20610](https://insights.sbomify.com/CVE-2021-20610/): Denial of service in MELIPC Series MI5122-VW (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-20611 and fix it if it is affected.

What it is: CVE-2021-20611 is a high-severity denial of service vulnerability in Mitsubishi Electric Corporation MELIPC Series MI5122-VW, published on 1 Dec 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-2021-20611 in the wild and no public exploit code.

Affected product: Mitsubishi Electric Corporation MELIPC Series MI5122-VW. 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-2021-20611/ (Markdown: https://insights.sbomify.com/CVE-2021-20611/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-20611
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-20611
- OSV: https://osv.dev/vulnerability/CVE-2021-20611

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From sbomify Insights: https://insights.sbomify.com/CVE-2021-20611/
Summaries are generated and may contain mistakes; the official description above is the record.