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Eibport FirmwareOperating system · Bab Technologie

CVE-2021-28911

CRITICAL · 9.8 CVSS v3.1 Published 2021-09-09
Fix available
A fix is available. Upgrade to 3.9.1 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
BAB TECHNOLOGIE GmbH eibPort V3 prior version 3.9.1 allow unauthenticated attackers access to /tmp path which contains some sensitive data (e.g. device serial number). Having those info, a possible loginId can be self-calculated in a brute force attack against BMX interface. This is usable and part of an attack chain to gain SSH root access.

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 eibPort V3 web server allows unauthenticated access to the /tmp directory, exposing sensitive device data including serial numbers. Attackers can use the exposed serial number to calculate a valid loginId and perform brute force attacks against the BMX interface, ultimately achieving SSH root access. This represents a critical attack chain vulnerability.

MitigationUpgrade eibPort V3 to version 3.9.1 or later to remediate the unauthenticated path traversal and protect sensitive data in /tmp.

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
Eibport FirmwareOperating system
Affected:< 3.9.1

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:3.1/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 eibPort V3 device on the network
    Locate the eibPort V3 web server by accessing its web interface via HTTP/HTTPS on the expected IP address or hostname. Note the device response and login page.
    Affected if The device is a Bab Technologie eibPort V3 with a web interface accessible on the network.
  2. Check the installed firmware version
    Log into the eibPort V3 web interface and navigate to the system information or firmware version page (typically found under Settings, System, or About). Alternatively, check the boot log or system status page for the firmware build number.
    Affected if The displayed firmware version is earlier than 3.9.1 (e.g., 3.9.0, 3.8.x, or older).
  3. Test for unauthenticated /tmp directory access
    Using a web browser or curl command, attempt to access the path traversal URL: http://[device-ip]/tmp/ or http://[device-ip]/..%2f/tmp/ to verify if the web server returns a directory listing or exposes files from the /tmp directory without authentication.
    Affected if The web server returns a directory listing or file contents from the /tmp directory without requiring login credentials.
  4. Check for exposed sensitive files in /tmp
    If /tmp access is possible, search for files containing serial numbers, credentials, or configuration files. Look for files with names like serial, device.conf, or similar patterns. Use commands like curl to enumerate common file paths such as /tmp/serial, /tmp/device_info, or /tmp/*.log.
    Affected if Files in /tmp contain device serial numbers, login credentials, or other sensitive information accessible without authentication.
  5. Verify if serial number exposure enables login calculation
    If a serial number is found, examine whether the web interface's login mechanism uses the serial number to derive or validate loginId values. Attempt a test login using the exposed serial number format described in the CVE.
    Affected if The exposed serial number can be used to calculate or validate a valid loginId for the BMX interface login.

The environment is affected if the eibPort V3 firmware is below version 3.9.1 AND the web server allows unauthenticated access to the /tmp directory, exposing sensitive data that can be used to calculate valid login credentials.

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 3.9.1 or later
Fixed in 3.9.1
Interim mitigation

Upgrade eibPort V3 to version 3.9.1 or later to remediate the unauthenticated path traversal and protect sensitive data in /tmp.

Recommended fix High confidence

3.9.1

  1. Verify current EibPort V3 firmware version via web interface or system status page
  2. Download firmware version 3.9.1 from official BAB TECHNOLOGIE GmbH source or authorized distributor
  3. Access EibPort device administration panel
  4. Navigate to firmware update or system maintenance section
  5. Upload and apply firmware version 3.9.1
  6. Verify successful installation by confirming new firmware version in system information
  7. Restart device if required by update process
  8. Confirm vulnerability is remediated by verifying /tmp path is no longer accessible without authentication

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

Fix this in Eibport Firmware Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,130
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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-2021-28911 in production — separate from our analysis above.

No notes yet

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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