dbcve.org
Bt 5 Series Cellular Router FirmwareOperating system · Sixnet

CVE-2016-4521

CRITICAL · 9.8 CVSS v3.0 Published 2016-05-31
Fix available
A fix is available. Upgrade to after 3.9.7 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

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 · unedited
Sixnet BT-5xxx and BT-6xxx M2M devices before 3.8.21 and 3.9.x before 3.9.8 have hardcoded credentials, which allows remote attackers to obtain access via unspecified vectors.

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 confidence

The Sixnet BT-5xxx and BT-6xxx M2M (Machine-to-Machine) devices contain hardcoded credentials embedded in the firmware that cannot be changed by administrators. This allows remote unauthenticated attackers to gain full administrative access to the devices over the network, potentially compromising the industrial control operations these devices support.

MitigationUpdate device firmware to version 3.8.21 (for 3.8.x branch) or 3.9.8 (for 3.9.x branch) or later to remove the hardcoded credentials. If immediate patching is not feasible, isolate affected devices behind firewalls and restrict network access to minimize exposure to external attackers.

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
Bt 5 Series Cellular Router FirmwareOperating system
Affected:<= 3.8.20<= 3.9.7
Bt 6 Series Cellular Router FirmwareOperating system
Affected:<= 3.8.20<= 3.9.7

CVSS 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
High
Integrity
High
Availability
High

CVSS:3.0/AV:N/AC:L/PR:N/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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify the Sixnet device model
    Locate the device physical label or log into the administrative web interface to confirm the exact model number (BT-5xxx or BT-6xxx series).
    Affected if The device model is a Sixnet BT-5xxx or BT-6xxx series cellular router.
  2. Retrieve the installed firmware version
    Log into the device web interface and navigate to the Status or System Information page to view the firmware version. Alternatively, access the device via console or SNMP to query the firmware version.
    Affected if Unable to retrieve firmware version from the device.
  3. Compare firmware version against affected ranges
    Check if the installed firmware version is <= 3.8.20 or <= 3.9.7. Note both the 3.8.x and 3.9.x branches are affected up to these versions.
    Affected if Firmware version is 3.8.20 or lower, or 3.9.7 or lower.
  4. Confirm hardcoded credentials cannot be changed
    Attempt to locate and modify any default credentials in the user management or system settings of the administrative interface. Note that this CVE describes credentials that are hardcoded and not modifiable by administrators.
    Affected if Default credentials exist and cannot be changed through the administrative interface.

The device is affected if it is a Sixnet BT-5xxx or BT-6xxx series router running firmware version 3.8.20 or lower, or 3.9.7 or lower, and contains hardcoded credentials that cannot be modified.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 · scoped
Upgrade available Upgrade to a release after 3.9.7
Interim mitigation

Update device firmware to version 3.8.21 (for 3.8.x branch) or 3.9.8 (for 3.9.x branch) or later to remove the hardcoded credentials. If immediate patching is not feasible, isolate affected devices behind firewalls and restrict network access to minimize exposure to external attackers.

Recommended fix High confidence

Firmware 3.8.21 or later (for 3.8.x branch); Firmware 3.9.8 or later (for 3.9.x branch)

  1. 1. Identify the current firmware version of the Sixnet BT-5xxx or BT-6xxx device by accessing the router's web interface or CLI
  2. 2. Determine which firmware branch is currently installed (3.8.x or 3.9.x)
  3. 3. Download the appropriate fixed firmware version from the vendor's official support site: upgrade to version 3.8.21 or later for the 3.8.x branch, or version 3.9.8 or later for the 3.9.x branch
  4. 4. Back up the current device configuration before performing the firmware upgrade
  5. 5. Upload and install the new firmware through the router's web interface or via TFTP/CLI method as documented in the vendor's manual
  6. 6. After upgrade, verify the new firmware version is installed and confirm the device is functioning normally
  7. 7. Change all default credentials immediately after the upgrade as a security best practice

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Bt 5 Series Cellular Router Firmware Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,980
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,168.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2016-4521 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2016-4521 in production — separate from our analysis above.

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.

What this is

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.

What belongs here
  • 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