CVE-2021-28846
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 · uneditedA Format String vulnerablity 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 of service due to a logic bug at address 0x40dcd0 when calling fprintf with "%s: key len = %d, too long\n" format. The two variables seem to be put in the wrong order. The vulnerability could be triggered by sending the POST request to apply_cgi with a long and unknown key in the request body.
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 format string vulnerability exists in TRENDnet TEW-755AP, TEW-755AP2KAC, TEW-821DAP2KAC, and TEW-825DAP firmware 1.11B03. The fprintf function at address 0x40dcd0 has variables in the wrong order within the format string '%s: key len = %d, too long\n', causing a logic bug that leads to denial of service when triggered via a POST request to apply_cgi with an excessively long key parameter.
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
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:L/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 modelCheck the device label, web interface status page, or SNMP inventory to confirm the exact model number (TEW-755AP, TEW-755AP2KAC, TEW-821DAP2KAC, or TEW-825DAP)Affected if The device model is one of the four affected models listed in the CVE
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Check the installed firmware versionAccess the device web interface, navigate to the status or system information page, and record the firmware version stringAffected if The firmware version is exactly 1.11B03 (no other versions are listed as affected)
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Verify the apply_cgi endpoint is reachableConfirm the device web management interface is accessible on the network (the vulnerability is triggered via POST request to apply_cgi)Affected if The web interface is exposed and the apply_cgi endpoint accepts requests with a key parameter
You are affected if your device is a TEW-755AP, TEW-755AP2KAC, TEW-821DAP2KAP, or TEW-825DAP running firmware version 1.11B03 and the web management interface with apply_cgi 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 dataContact TRENDnet for available firmware updates that address this vulnerability; apply the vendor-supplied patch to all affected devices. If no update is available, consider network segmentation or disabling the apply_cgi endpoint as a temporary workaround.
- Consultation3.0 h
- Implementation2.0 h
- Testing3.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-28846 — 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-2021-28846 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
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