CVE-2021-20166
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 · uneditedNetgear RAX43 version 1.0.3.96 contains a buffer overrun vulnerability. The URL parsing functionality in the cgi-bin endpoint of the router containers a buffer overrun issue that can redirection control flow of the applicaiton.
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 confidenceA buffer overrun vulnerability exists in the URL parsing functionality of the cgi-bin endpoint on Netgear RAX43 router firmware version 1.0.3.96. The vulnerability allows an attacker to potentially redirect application control flow, likely through malformed URL input that overflows a buffer.
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= 1.0.3.96CVSS 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
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:A/AC:L/PR:N/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 router modelCheck the device label on the router or log into the web management interface to confirm the model number is RAX43Affected if Model is not Netgear RAX43 - different models are not affected by this specific CVE
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Check firmware versionLog into the router web interface (typically at 192.168.1.1), navigate to Administration > Firmware Update or Advanced > Administration > Router Update, and record the current firmware versionAffected if Firmware version is exactly 1.0.3.96 - only this exact version is affected
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Verify cgi-bin endpoint accessibilityAttempt to access http://<router-ip>/cgi-bin/ from a client on the network to confirm the endpoint is reachableAffected if The cgi-bin endpoint responds - the buffer overflow occurs in URL parsing of this endpoint
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Check web interface exposureDetermine if the router web management interface (port 80/443) is exposed to untrusted networks by reviewing firewall rules or attempting access from an external IPAffected if Web interface is exposed to untrusted networks - this increases likelihood of exploit attempts
You are affected only if you have a Netgear RAX43 router running exactly firmware version 1.0.3.96 and the cgi-bin endpoint is accessible.
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 available firmware updates from Netgear for the RAX43 model; if no update is available, restrict network access to the router's web management interface to reduce attack surface.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,600.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-20166 — 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-2021-20166 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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