CVE-2021-28843
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 · uneditedNull Pointer Dereference vulnerability exists in TRENDnet TEW-755AP 1.11B03, TEW-755AP2KAC 1.11B03, TEW-821DAP2KAC 1.11B03, and TEW-825DAP 1.11B03 by sending the POST request to apply_cgi with an unknown action name.
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 confidenceA null pointer dereference vulnerability exists in the web interface of multiple TRENDnet access point models. The vulnerability is triggered by sending a POST request to the apply_cgi endpoint with an unrecognized or unknown action name parameter, causing the device to crash or potentially allow further exploitation.
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= 1.11b03= 1.11b03= 1.11b03= 1.11b03CVSS 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
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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 TRENDnet access point modelCheck the device label, web interface, or network discovery for the exact model number (Tew 755ap, Tew 755ap2kac, Tew 821dap2kac, or Tew 825dap)Affected if The device is not one of these four models - other TRENDnet devices are not affected by this CVE
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Check the installed firmware versionLog into the web interface and navigate to the Status or System Information page to view the firmware version, or check via SNMP or the device's administration CLI if availableAffected if The firmware version is not exactly 1.11b03 - only version 1.11b03 is listed as affected
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Confirm the exact version matches 1.11b03Compare the displayed firmware version string to '1.11b03' - note that this is an exact version match, not a rangeAffected if The version string differs by even a single character from 1.11b03
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Verify the web interface is network-accessibleCheck if TCP port 80 or 443 (HTTP/HTTPS) is open and reachable on the device from your detection locationAffected if The web interface is not accessible at all - the vulnerability requires the web interface to be reachable to be exploitable
Your environment is affected if you have a TRENDnet Tew 755ap, Tew 755ap2kac, Tew 821dap2kac, or Tew 825dap device running exactly firmware version 1.11b03 with the web interface exposed on the network.
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-supplied firmware updates when available; until then, restrict web interface access to trusted networks or IP addresses, and monitor for unusual apply_cgi requests.
- Consultation2.0 h
- Implementation1.0 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 $1,696.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-28843 — 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-2021-28843 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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