CVE-2021-20854
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedELECOM LAN routers (WRH-733GBK firmware v1.02.9 and prior and WRH-733GWH firmware v1.02.9 and prior) allows a network-adjacent attacker with an administrator privilege to execute arbitrary OS commands via unspecified vectors.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · moderate confidenceELECOM WRH-733GBK and WRH-733GWH LAN routers firmware v1.02.9 and prior contain an OS command injection vulnerability (CWE-78). An attacker with network adjacency and valid administrator credentials can execute arbitrary operating system commands on the affected device through unspecified vectors.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data<= 1.02.9<= 1.02.9CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Adjacent
- Complexity
- Low
- Privileges
- High
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:A/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify the device modelCheck the product label on the router or access the router's web administration interface and look for the model number (WRH-733GBK or WRH-733GWH)Affected if The device is not one of these two models, the vulnerability does not apply
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Check the firmware versionLog into the router web interface and navigate to the system status or firmware information page. Alternatively, check the firmware file if you have access to it, or use the router's administration CLI if available.Affected if The firmware version is 1.02.9 or lower, the device is affected by this CVE
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Verify network accessibilityDetermine if the router management interface is accessible from the network segment where untrusted devices operate. Check if the router's web interface (typically on ports 80/443 or custom ports) responds to requests from non-local IP addresses.Affected if The router admin interface is exposed to network segments beyond the trusted local network, an attacker with network adjacency could potentially reach it
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Assess credential securityReview whether default administrator credentials are still in use, or check if weak/simple credentials have been configured. Attempt to determine if credentials could be easily guessed or obtained.Affected if Default credentials or weak passwords are in use, an attacker who obtains valid admin credentials could exploit the command injection
A user is affected if they have an ELECOM WRH-733GBK or WRH-733GWH router running firmware version 1.02.9 or lower, and the router admin interface is accessible from a network where an attacker has adjacency, especially if default or weak admin credentials are in use.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataApply vendor firmware update to version v1.02.9 or later. If no update is available, consider network segmentation to limit exposure and enforce strong administrator credentials to reduce credential theft risk.
- Consultation2.0 h
- Implementation3.0 h
- Testing2.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-20854 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-20854 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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