CVE-2017-6030
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 predictable value range from previous values issue was discovered in Schneider Electric Modicon PLCs Modicon M221, firmware versions prior to Version 1.5.0.0, Modicon M241, firmware versions prior to Version 4.0.5.11, and Modicon M251, firmware versions prior to Version 4.0.5.11. The affected products generate insufficiently random TCP initial sequence numbers that may allow an attacker to predict the numbers from previous values. This may allow an attacker to spoof or disrupt TCP connections.
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 confidenceSchneider Electric Modicon M221, M241, and M251 PLCs generate insufficiently random TCP initial sequence numbers, allowing attackers to predict ISN values from previous observations. This predictability enables TCP connection spoofing or disruption attacks against the PLC's network communications.
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<= 4.0.3.20<= 4.0.3.20<= 1.1.1.5CVSS 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
- Low
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
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 the Modicon PLC modelLocate the PLC hardware label or check project configuration in SoMachine/EcoStruxure Machine Expert to confirm whether the device is an M221, M241, or M251 controllerAffected if Device is not one of these three models (M221, M241, M251)
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Check the PLC firmware versionAccess the PLC via Schneider programming software (SoMachine/EcoStruxure Machine Expert), web interface, or console cable, then navigate to the firmware/version information screen to read the installed firmware build numberAffected if Firmware version is <= 1.1.1.5 for M221, or <= 4.0.3.20 for M241 or M251
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Verify TCP/IP communication is enabledIn the PLC programming software, expand the PLC configuration tree and check whether Ethernet, Modbus TCP, or other TCP-based communication services are configured and activeAffected if TCP/IP stack is not present or completely disabled on the PLC
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Assess network accessibility of the PLCReview network architecture and firewall rules to determine whether the PLC's TCP ports (especially port 502 for Modbus/TCP) are exposed to untrusted or external networksAffected if PLC TCP ports are reachable from untrusted network segments or the internet
You are affected if you have a Modicon M221 with firmware <= 1.1.1.5, or an M241/M251 with firmware <= 4.0.3.20, and TCP/IP networking is enabled and accessible to potential attackers.
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 dataUpdate PLC firmware to Version 1.5.0.0 (M221) or Version 4.0.5.11 (M241/M251). If immediate patching is not feasible, implement network segmentation and firewall controls to limit exposure to untrusted networks.
- Consultation6.0 h
- Implementation12.0 h
- Testing8.0 h
- Review / QA4.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2017-6030 — 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-2017-6030 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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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
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