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Ccu3 FirmwareOperating system · Eq 3

CVE-2019-10121

CRITICAL · 9.8 CVSS v3.0 Published 2019-07-10
Fix available
A fix is available. Upgrade to 2.41.8 / 3.43.15 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
eQ-3 HomeMatic CCU2 devices before 2.41.8 and CCU3 devices before 3.43.15 use session IDs for authentication but lack authorization checks. An attacker can obtain a session ID via the user authentication dialogue, aka HMCCU-153. This leads to automatic login as admin.

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

eQ-3 HomeMatic CCU2 and CCU3 devices use session IDs for authentication but fail to perform proper authorization checks on those sessions. An attacker can obtain a valid session ID through the user authentication dialogue, and the system automatically grants admin privileges to that session without validating authorization, leading to full administrative access.

MitigationUpdate HomeMatic CCU2 firmware to version 2.41.8 or later, and CCU3 firmware to version 3.43.15 or later, to include the authorization check fix.

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
Ccu3 FirmwareOperating system
Affected:< 3.43.15
Ccu2 FirmwareOperating system
Affected:< 2.41.8

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 device model
    Check if the device is an eQ-3 HomeMatic CCU2 or CCU3 by reviewing the device label, documentation, or checking the web interface login page for model identification.
    Affected if The device is a CCU2 or CCU3 unit.
  2. Check CCU3 firmware version
    Access the web interface, navigate to 'System Settings' then 'System Information', or run '/usr/bin/env /usr/local/etc/config/RFD status' via SSH to retrieve the firmware version.
    Affected if The firmware version is lower than 3.43.15.
  3. Check CCU2 firmware version
    Access the web interface, navigate to 'System Settings' then 'System Information', or run '/usr/bin/env /usr/local/etc/config/RFD status' via SSH to retrieve the firmware version.
    Affected if The firmware version is lower than 2.41.8.
  4. Verify web interface accessibility
    Attempt to reach the device's web interface on port 80 or 443 from a network location. Check router port forwarding rules or firewall settings that may expose the CCU web interface externally.
    Affected if The web interface is accessible from untrusted networks or the internet.

A user is affected if they have a CCU2 with firmware below 2.41.8 or a CCU3 with firmware below 3.43.15, particularly if the web interface is accessible beyond trusted local networks.

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 2.41.8 / 3.43.15 or later
Fixed in 2.41.83.43.15
Interim mitigation

Update HomeMatic CCU2 firmware to version 2.41.8 or later, and CCU3 firmware to version 3.43.15 or later, to include the authorization check fix.

Recommended fix High confidence

CCU2 Firmware >= 2.41.8 | CCU3 Firmware >= 3.43.15

  1. 1. Access the CCU web interface by entering the device's IP address in a web browser
  2. 2. Log in with administrator credentials
  3. 3. Navigate to 'Settings' > 'System Settings' (or 'Einstellungen' > 'Systemeinstellungen' in German)
  4. 4. Click on 'Firmware Update' or 'Software Update' (or 'Firmware-Update')
  5. 5. Check for available updates and proceed with installing the latest firmware
  6. 6. Ensure the firmware version is at least 2.41.8 for CCU2 or at least 3.43.15 for CCU3
  7. 7. Verify the update was successful by checking the firmware version in 'Status' > 'Device Information'

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

Fix this in Ccu3 Firmware Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA2.0 h
18.0 hours of engineering $3,200
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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-2019-10121 in production — separate from our analysis above.

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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
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  • No spam, self-promotion, credentials, or personal data