CVE-2021-42851
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 vulnerability was reported in some Lenovo Personal Cloud Storage devices that could allow an unauthenticated user to create a standard user account.
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 · moderate confidenceThis vulnerability in Lenovo Personal Cloud Storage devices allows an unauthenticated attacker to bypass authentication mechanisms and create a standard user account. This represents an authentication/authorization bypass flaw that could enable unauthorized access to the storage system.
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< 5.3.6.a1< 5.3.6.t1< 5.3.8.x1< 5.3.8.t2< 5.3.7.t2-proCVSS 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
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
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 your Lenovo Personal Cloud Storage modelLocate the device model number on the physical device label or in the device administration interface under System Information or Device StatusAffected if The model is an A1, T1, X1, T2, or T2pro unit
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Check the installed firmware versionAccess the device admin interface, navigate to Settings or System Update, and record the firmware version number displayedAffected if Firmware version is below 5.3.6.a1 for A1, below 5.3.6.t1 for T1, below 5.3.8.x1 for X1, below 5.3.8.t2 for T2, or below 5.3.7.t2-pro for T2pro
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Review user accounts for unauthorized entriesIn the device admin interface, go to User Management or Users section and list all standard user accounts. Compare against known legitimate accounts you createdAffected if Any standard user account exists that you did not intentionally create
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Examine logs for account creation eventsAccess the device logging or audit logs through the admin interface or system logs. Search for events related to user account creation, especially from external IP addresses or during unexpected time periodsAffected if Logs show user account creation events from unauthenticated or unexpected sources
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Check network exposure of management interfaceVerify whether the device management interface is accessible from untrusted networks or the public internet by reviewing firewall rules or port forwarding configurationsAffected if The admin interface is exposed to untrusted networks without proper access controls
You are affected if you have a Lenovo Personal Cloud Storage device (A1, T1, X1, T2, or T2pro) running firmware below the patched versions AND either unauthorized user accounts exist or the device is network-accessible to untrusted parties.
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.
dbcve · scoped5.3.6.t15.3.6.a15.3.7.t2-pro
Apply the vendor-supplied firmware update from Lenovo to address the authentication bypass. If patches are unavailable, restrict network access to the device management interface and monitor for unauthorized account creation.
A1: >=5.3.6.a1 | T1: >=5.3.6.t1 | X1: >=5.3.8.x1 | T2: >=5.3.8.t2 | T2pro: >=5.3.7.t2-pro
- 1. Identify the specific Lenovo Personal Cloud Storage model (A1, T1, X1, T2, or T2pro) in use
- 2. Access the device administration interface through its web portal or mobile app
- 3. Navigate to the System Settings or Firmware Update section
- 4. Check the current firmware version under About or System Information
- 5. Download the appropriate fixed firmware from Lenovo's support site (iknow.lenovo.com.cn): For A1 use version 5.3.6.a1 or later, for T1 use 5.3.6.t1 or later, for X1 use 5.3.8.x1 or later, for T2 use 5.3.8.t2 or later, for T2pro use 5.3.7.t2-pro or later
- 6. Upload the firmware file through the web interface or mobile app
- 7. Wait for the firmware upload and installation to complete - do not power off the device during this process
- 8. After reboot, verify the new firmware version is installed
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation3.0 h
- Implementation4.0 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-2021-42851 — 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-2021-42851 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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