# CVE-2021-20739: Command injection in WRC-300FEBK, WRC-F300NF, WRC-733FEBK, WRH-300RD, WRH-300BK, WRH-300SV, WRH-300WH, WRH-H300WH, WRH-H300BK, WRH-300BK-S, and WRH-300WH-S

> Unauthenticated network-adjacent attackers can execute arbitrary OS commands on ELECOM wireless routers, potentially compromising the device.

- **Severity:** High 8.8 (`CVSS:3.1/AV:A/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:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 7 Jul 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-6g7g-h77w-72mh

## What is CVE-2021-20739?

CVE-2021-20739 is a high-severity command injection vulnerability in ELECOM CO.,LTD. WRC-300FEBK, WRC-F300NF, WRC-733FEBK, WRH-300RD, WRH-300BK, WRH-300SV, WRH-300WH, WRH-H300WH, WRH-H300BK, WRH-300BK-S, and WRH-300WH-S, published on 7 Jul 2021. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

WRC-300FEBK, WRC-F300NF, WRC-733FEBK, WRH-300RD, WRH-300BK, WRH-300SV, WRH-300WH, WRH-H300WH, WRH-H300BK, WRH-300BK-S, and WRH-300WH-S all versions allows an unauthenticated network-adjacent attacker to execute an arbitrary OS command via unspecified vectors.

Weakness: CWE-78 (Improper Neutralization of Special Elements used in an OS Command)

## Which versions are affected by CVE-2021-20739?

It affects 11 products.


Products: Elecom Wrc-300febk Firmware, Elecom Wrc-733febk Firmware, Elecom Wrc-F300nf Firmware, Elecom Wrh-300bk-S Firmware, Elecom Wrh-300bk Firmware, Elecom Wrh-300rd Firmware, Elecom Wrh-300sv Firmware, Elecom Wrh-300wh-S Firmware, Elecom Wrh-300wh Firmware, Elecom Wrh-H300bk Firmware, Elecom Wrh-H300wh Firmware.

## How do I fix CVE-2021-20739?

No fix has been published for CVE-2021-20739 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-20739 being exploited?

There is no known exploitation of CVE-2021-20739 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-20739 and fix it if it is affected.

What it is: CVE-2021-20739 is a high-severity command injection vulnerability in ELECOM CO.,LTD. WRC-300FEBK, WRC-F300NF, WRC-733FEBK, WRH-300RD, WRH-300BK, WRH-300SV, WRH-300WH, WRH-H300WH, WRH-H300BK, WRH-300BK-S, and WRH-300WH-S, published on 7 Jul 2021. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-20739 in the wild and no public exploit code.

Affected product: ELECOM CO.,LTD. WRC-300FEBK, WRC-F300NF, WRC-733FEBK, WRH-300RD, WRH-300BK, WRH-300SV, WRH-300WH, WRH-H300WH, WRH-H300BK, WRH-300BK-S, and WRH-300WH-S. 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-2021-20739/ (Markdown: https://insights.sbomify.com/CVE-2021-20739/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-20739
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-20739
- OSV: https://osv.dev/vulnerability/CVE-2021-20739

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-20739/
Summaries are generated and may contain mistakes; the official description above is the record.