CVE-2016-3949
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 · uneditedSiemens SIMATIC S7-300 Profinet-enabled CPU devices with firmware before 3.2.12 and SIMATIC S7-300 Profinet-disabled CPU devices with firmware before 3.3.12 allow remote attackers to cause a denial of service (defect-mode transition) via crafted (1) ISO-TSAP or (2) Profibus packets.
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 confidenceThe vulnerability allows remote attackers to send specially crafted ISO-TSAP or Profibus packets to SIMATIC S7-300 CPU devices, causing an uncontrolled defect-mode transition and resulting in denial of service. Affected devices include both Profinet-enabled CPUs before firmware 3.2.12 and Profinet-disabled CPUs before firmware 3.3.12.
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= 3.2.11= 3.3.11CVSS 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
- None
- Availability
- High
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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.
-
Identify the SIMATIC S7-300 CPU deviceAccess the PLC hardware configuration via TIA Portal or STEP 7, or check the device nameplate and model number on the physical CPU module. Confirm it is a Simatic S7-300 series CPU.Affected if The device is not a SIMATIC S7-300 CPU - this CVE does not apply.
-
Check the firmware version on the CPUIn TIA Portal or STEP 7, go to the CPU properties and locate the firmware version field, or access the CPU's online diagnostics. Record the firmware version number.Affected if The firmware version is 3.2.11 or lower for Profinet-enabled units, or 3.3.11 or lower for Profinet-disabled units.
-
Determine if Profinet is enabledIn the TIA Portal/STEP 7 hardware configuration, check the CPU network settings for Profinet interface configuration, or inspect the PN interface parameters in the CPU properties.Affected if The device has Profinet enabled (firmware 3.2.x affected up to 3.2.11) or disabled (firmware 3.3.x affected up to 3.3.11).
-
Verify network exposure of ISO-TSAP and Profibus portsReview firewall rules and network segmentation to determine if ports 102 (ISO-TSAP) and the Profibus interface are accessible from untrusted networks. Use port scanning or network documentation to confirm.Affected if Port 102/ISO-TSAP or Profibus interfaces are directly accessible from external or untrusted network segments.
The device is affected if it is a SIMATIC S7-300 CPU with firmware 3.2.11 or lower (Profinet-enabled) or 3.3.11 or lower (Profinet-disabled), and the ISO-TSAP or Profibus ports are network-accessible.
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 dataUpgrade SIMATIC S7-300 CPU firmware to version 3.2.12 or later (Profinet-enabled) or 3.3.12 or later (Profinet-disabled). If immediate patching is not feasible, implement network segmentation and restrict access to industrial protocol ports (ISO-TSAP 102, Profibus) via firewalls to limit attack surface.
- Consultation4.0 h
- Implementation16.0 h
- Testing8.0 h
- Review / QA4.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $8,960.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2016-3949 — 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-2016-3949 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
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.
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
- No spam, self-promotion, credentials, or personal data