CVE-2021-28841
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 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 by sending a POST request to apply_cgi via an action ping_test without a ping_ipaddr 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 TRENDnet wireless access points (TEW-755AP, TEW-755AP2KAC, TEW-821DAP2KAC, TEW-825DAP) firmware 1.11B03. When a remote attacker sends a crafted POST request to apply_cgi with action=ping_test but omits the ping_ipaddr parameter, the application attempts to dereference a null pointer, causing a denial of service (device crash).
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.
-
Identify the device modelCheck the physical device label or access the web management interface to confirm the model number is one of: TEW-755AP, TEW-755AP2KAC, TEW-821DAP2KAC, or TEW-825DAPAffected if The device model matches one of the four affected models listed in the CVE
-
Check the installed firmware versionLog into the device web interface and navigate to the Status or System Information page to view the firmware version. Compare it to 1.11B03Affected if The firmware version is exactly 1.11B03
-
Verify web management interface is accessibleAttempt to access the device web interface over HTTP/HTTPS from the network segment where the device is deployedAffected if The web interface is reachable, indicating the attack surface exists
-
Confirm ping_test functionality is presentExamine if the apply_cgi endpoint accepts the action=ping_test parameter by reviewing the web interface or testing with a benign requestAffected if The ping_test action is available in the apply_cgi endpoint, enabling the vulnerable code path
You are affected if your device is a TRENDnet TEW-755AP, TEW-755AP2KAC, TEW-821DAP2KAP, or TEW-825DAP running firmware version 1.11B03 and the web management interface 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 dataApply vendor firmware updates if available; otherwise, restrict access to the device's web management interface to trusted networks or disable the ping_test functionality via access controls.
- Consultation3.0 h
- Implementation4.0 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 $2,880.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-28841 — 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-2021-28841 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
Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.
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
- No spam, self-promotion, credentials, or personal data