CVE-2021-28842
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 Deference vulnerability exists in TRENDnet TEW-755AP 1.11B03, TEW-755AP2KAC 1.11B03, TEW-821DAP2KAC 1.11B03, and TEW-825DAP 1.11B03, which could let a remote malicious user cause a denial os service by sending the POST request to apply_cgi via action do_graph_auth without login_name key.
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 management interface of multiple TRENDnet wireless access point models (TEW-755AP, TEW-755AP2KAC, TEW-821DAP2KAP, TEW-825DAP) running firmware 1.11B03. The vulnerability is triggered by sending a specially crafted POST request to apply_cgi with the action parameter set to do_graph_auth while omitting the login_name parameter, causing the device to crash and resulting in 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= 1.11b03= 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 device modelAccess the device web management interface and navigate to the Status or System Information page, or check the device label, to confirm the exact model number (TEW-755AP, TEW-755AP2KAC, TEW-821DAP2KAP, or TEW-825DAP)Affected if The device model is one of the four listed models and the version is 1.11B03
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Check the installed firmware versionIn the device web interface, go to Administration > Firmware Upgrade or System > Version to view the current firmware versionAffected if The firmware version is exactly 1.11B03 (exact match per the affected version range)
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Verify the web management interface is accessibleAttempt to access the device IP on HTTP/HTTPS ports 80 or 443 from the network segment where the check is performedAffected if The web interface responds to requests, meaning the attack surface is present
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Check if apply_cgi endpoint accepts requestsSend a POST request to http://[device-ip]/apply_cgi with action=do_graph_auth and verify the endpoint responds (note: do not include login_name parameter to test the vulnerability condition)Affected if The apply_cgi endpoint accepts POST requests with the action parameter, exposing the vulnerable code path
The device is affected if it is a TEW-755AP, TEW-755AP2KAC, TEW-821DAP2KAP, or TEW-825DAP running firmware version 1.11B03 and the web management interface is accessible to the attacker.
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 the vendor-supplied firmware update to resolve the vulnerability. Until patched, restrict access to the device's web management interface using firewall rules or ACLs to prevent unauthorized remote attackers from exploiting this flaw.
- Consultation2.0 h
- Implementation3.0 h
- Testing2.0 h
- Review / QA1.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2021-28842 — 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-2021-28842 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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