CVE-2018-16221
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 · uneditedThe diagnostics web interface in the Yeahlink Ultra-elegant IP Phone SIP-T41P (firmware 66.83.0.35) does not validate (escape) the path information (path traversal), which allows an authenticated remote attacker to get access to privileged information (e.g., /etc/passwd) via path traversal (relative path information in the file parameter of the corresponding POST request).
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 confidenceThe diagnostics web interface in Yealink SIP-T41P IP phones (firmware 66.83.0.35) lacks proper input validation on the file parameter in POST requests, allowing authenticated attackers to use path traversal sequences (e.g., ../../etc/passwd) to read sensitive files outside the intended web root directory.
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= 66.83.0.35CVSS 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
- Adjacent
- Complexity
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.0/AV:A/AC:L/PR:L/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 the device modelCheck if the device is a Yealink SIP-T41P IP phone by logging into the web interface or checking the device labelAffected if Device is not a Yealink SIP-T41P - not affected by this specific CVE
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Check the firmware versionLog into the phone web interface and navigate to Status or Settings > Firmware to view the installed firmware versionAffected if Firmware version is NOT exactly 66.83.0.35 - the specific version required for this vulnerability is not installed
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Verify diagnostics interface accessibilityAttempt to access the diagnostics web interface - typically found at /servlet?com=... or a diagnostics CGI endpoint on the phone's web serverAffected if The diagnostics functionality is not exposed or accessible via the web interface
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Confirm authentication statusCheck whether the web management interface requires authentication and whether valid credentials can be obtainedAffected if Web interface has no authentication configured, though the CVE description indicates authenticated attackers are required
A user is affected only if they have a Yealink SIP-T41P with firmware version exactly 66.83.0.35, the diagnostics web interface is accessible, and an attacker can obtain valid credentials for the web management interface.
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 update when available; until then, restrict access to the web management interface to trusted networks or IPs only, and consider disabling the diagnostics functionality if not required.
- Consultation3.0 h
- Implementation4.0 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 $3,408.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2018-16221 — 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-2018-16221 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
- No weaponised exploit code, or anything meant to cause harm
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