CVE-2021-20855
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 · uneditedCross-site scripting vulnerability in ELECOM LAN routers (WRH-733GBK firmware v1.02.9 and prior and WRH-733GWH firmware v1.02.9 and prior) allows a remote authenticated attacker to inject an arbitrary script 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 confidenceCross-site scripting (XSS) vulnerability in ELECOM LAN routers WRH-733GBK and WRH-733GWH (firmware v1.02.9 and prior) allows a remote authenticated attacker to inject arbitrary JavaScript code through unspecified vectors. This stored XSS could execute in the context of other users accessing the router's web interface.
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
- Network
- Complexity
- Low
- Privileges
- Low
- User interaction
- Required
- Scope
- Changed
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
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 router modelCheck the product label on the physical router device or log into the web management interface to confirm the exact model numberAffected if Model is WRH-733GBK or WRH-733GWH
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Check the installed firmware versionAccess the router web administration panel (commonly at 192.168.1.1 or 192.168.0.1) and navigate to the firmware or system status section to view the installed firmware versionAffected if Firmware version is 1.02.9 or earlier
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Confirm remote administration is enabledIn the router web interface, check the administration or remote management settings to see if the web interface is accessible from external networksAffected if Remote administration is enabled and the interface is accessible from untrusted networks
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Review configuration fields for injected scriptsExamine all user-configurable fields in the router web interface (such as network names, descriptions, or administrative settings) for any unexpected script tags or JavaScript code that may have been storedAffected if Suspicious JavaScript code or script tags are found in any router configuration fields
The environment is affected if the router is an ELECOM WRH-733GBK or WRH-733GWH running firmware version 1.02.9 or earlier, with the web management interface accessible to an authenticated attacker who could inject the stored XSS payload
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 dataUpdate the router firmware to a version newer than 1.02.9 when released by ELECOM. If no update is available, restrict administrative access to trusted IP addresses and monitor for unauthorized access.
- Consultation2.0 h
- Implementation2.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,984.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-20855 — 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-2021-20855 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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- 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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