CVE-2019-6816
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 · uneditedIn Modicon Quantum all firmware versions, a CWE-94: Code Injection vulnerability could cause an unauthorized firmware modification with possible Denial of Service when using Modbus protocol.
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 confidenceA CWE-94 code injection vulnerability in Schneider Electric Modicon Quantum PLCs allows remote attackers to modify firmware without authentication via the Modbus protocol, potentially causing unauthorized firmware changes and denial of service.
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 dataall versionsCVSS 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
- High
- Availability
- High
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/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 Modicon Quantum PLCs on the networkScan the network for Modicon Quantum devices using industrial asset inventory tools, or review network diagrams and PLC configuration files for Modicon Quantum controller IP addresses and MAC addresses with vendor OUI 00:1B:4B or similarAffected if Any Modicon Quantum PLC is present in the environment
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Verify Modbus protocol exposureCheck network firewall rules and PLC network configuration to determine if TCP/502 (Modbus) or UDP/502 is accessible from unauthorized network segments or the internetAffected if Modbus/TCP port 502 is open to untrusted networks or unauthorized endpoints
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Check for unauthorized firmware modificationsConnect to the PLC using Schneider Electric programming software (Unity Pro or equivalent) and verify the firmware hash/signature against known-good baseline documentation, or review firmware version logs stored in the engineering workstationAffected if The installed firmware version does not match the expected baseline or shows unexpected modification timestamps
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Detect suspicious Modbus trafficCapture and analyze Modbus traffic using a network sniffer or IDS/IPS looking for Write Multiple Registers (function code 0x10) or other firmware update function codes targeting the firmware upload memory areaAffected if Modbus traffic contains write operations to firmware upload registers or unexpected configuration changes from unauthorized sources
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Review PLC access control logsExamine PLC event logs or network authentication logs for failed authentication attempts on firmware update functions, or check for connections from unknown IP addresses using ModbusAffected if There are connection attempts or commands from unauthorized IP addresses, or authentication bypass events in the logs
The environment is affected if any Modicon Quantum PLC with Modbus accessibility is present, regardless of firmware version, since all versions are vulnerable to unauthorized firmware modification via Modbus.
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 dataImplement network segmentation to isolate ICS assets, restrict Modbus access to authorized endpoints, and apply vendor-provided firmware patches when available; until patched, monitor for unauthorized Modbus traffic.
- Consultation8.0 h
- Implementation16.0 h
- Testing12.0 h
- Review / QA6.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $11,776.
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Free · runs locallyCheck whether your project pulls in CVE-2019-6816 — 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-2019-6816 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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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.
- 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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