CVE-2018-21135
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 · uneditedCertain NETGEAR devices are affected by a stack-based buffer overflow by an authenticated user. This affects R6700 before 1.0.1.48, R7500 before 1.0.0.124, R7800 before 1.0.2.58, R8900 before 1.0.4.2, R9000 before 1.0.4.2, WNDR3700v4 before 1.0.2.102, WNDR4300v1 before 1.0.2.104, WNDR4300v2 before 1.0.0.56, WNDR4500v3 before 1.0.0.56, and WNR2000v5-R2000 before 1.0.0.68.
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 · high confidenceStack-based buffer overflow vulnerability in multiple NETGEAR router models (R6700, R7500, R7800, R8900, R9000, WNDR3700v4, WNDR4300v1, WNDR4300v2, WNDR4500v3, WNR2000v5-R2000) that can be exploited by an authenticated user, potentially allowing arbitrary code execution or denial of service.
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< 1.0.1.48< 1.0.0.124< 1.0.2.58< 1.0.4.2< 1.0.4.2< 1.0.2.102< 1.0.2.104< 1.0.0.56< 1.0.0.56CVSS 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
- High
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/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 router modelLocate the model number on the device label or check in the router web interface under System or Status settingsAffected if Model is R6700, R7500, R7800, R8900, R9000, WNDR3700v4, WNDR4300v1, WNDR4300v2, WNDR4500v3, or WNR2000v5-R2000
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Determine firmware versionAccess the router web interface (typically 192.168.1.1), log in, and navigate to Administration > Firmware Update or Router Status to view the current firmware versionAffected if Firmware version cannot be determined or the displayed version is below the patched threshold for your model
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Compare version against affected rangesMatch your firmware version to the following thresholds: R6700 < 1.0.1.48, R7500 < 1.0.0.124, R7800 < 1.0.2.58, R8900/R9000 < 1.0.4.2, WNDR3700v4 < 1.0.2.102, WNDR4300v1 < 1.0.2.104, WNDR4300v2/WNDR4500v3 < 1.0.0.56Affected if Installed firmware version is lower than the specified threshold for your exact router model
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Verify administrative interface exposureCheck router settings for remote management or web access from WAN, and test if the admin interface (port 80/443) is reachable from outside your local network using a port scannerAffected if Administrative interface is accessible from untrusted networks or the internet
Your environment is affected if you are running one of the listed router models with firmware below the specified version threshold and the administrative interface is accessible to untrusted users.
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 data1.0.0.561.0.0.1241.0.1.48
Update affected devices to the specified firmware versions (R6700: 1.0.1.48, R7500: 1.0.0.124, R7800: 1.0.2.58, R8900/R9000: 1.0.4.2, WNDR3700v4: 1.0.2.102, WNDR4300v1: 1.0.2.104, WNDR4300v2/WNDR4500v3: 1.0.0.56, WNR2000v5-R2000: 1.0.0.68). If firmware updates are unavailable, restrict administrative interface access to trusted networks.
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2018-21135 — 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-2018-21135 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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