CVE-2021-20149
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 · uneditedTrendnet AC2600 TEW-827DRU version 2.08B01 does not have sufficient access controls for the WAN interface. The default iptables ruleset for governing access to services on the device only apply to IPv4. All services running on the devices are accessible via the WAN interface via IPv6 by default.
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 confidenceTrendnet TEW-827DRU firmware 2.08B01 has a critical access control gap where iptables firewall rules only filter IPv4 traffic. All device services (web UI, SSH, etc.) are accessible from the WAN interface via IPv6 by default, as no corresponding ip6tables rules exist.
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= 2.08b01CVSS 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
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/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 device modelLog into the device web UI or SSH and check the model name in System Status or the equivalent pageAffected if Device is not a Trendnet TEW-827DRU - the CVE does not apply to other models
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Check firmware versionNavigate to the firmware version information page in the web UI or run 'cat /proc/version' or 'nvram get firmver' via SSHAffected if Firmware version is not exactly 2.08B01 - only version 2.08B01 is listed as affected
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Verify IPv6 is enabled on WAN interfaceCheck the IPv6 configuration in the WAN settings page of the web UI, or run 'ip -6 addr show' or check network configuration files via SSHAffected if IPv6 is not enabled on the WAN - the vulnerability requires IPv6 to be active
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Check for ip6tables rulesRun 'ip6tables -L' or 'ip6tables -L -n -v' via SSH to list all IPv6 firewall rulesAffected if No ip6tables rules exist or the default policy is ACCEPT for all chains, meaning WAN IPv6 traffic is unfiltered
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Confirm WAN-facing services are reachable via IPv6From an external IPv6-capable host, attempt to reach the device services (HTTP port 80, HTTPS port 443, SSH port 22) using the WAN IPv6 addressAffected if Device services are accessible from WAN over IPv6 - this confirms the exposure exists
A device is affected if it is a Trendnet TEW-827DRU running firmware 2.08B01 with IPv6 enabled on the WAN and no ip6tables rules blocking inbound connections.
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 dataImplement IPv6 firewall rules to restrict WAN-facing services, or disable IPv6 on the WAN interface if not required, to align IPv6 access controls with the existing IPv4 iptables policy.
- Consultation3.0 h
- Implementation6.0 h
- Testing3.0 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 $3,984.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-20149 — 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-2021-20149 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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- Version or environment caveats, and links to real fixes
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