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Simatic S7 300 Cpu FirmwareOperating system · Siemens

CVE-2016-9158

HIGH · 7.5 CVSS v3.1 Published 2016-12-17
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
84/100
Remediation priority · High
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
A vulnerability has been identified in SIMATIC S7-300 CPU family (All versions), SIMATIC S7-300 CPU family (incl. related ET200 CPUs and SIPLUS variants) (All versions), SIMATIC S7-400 PN/DP V6 and below CPU family (incl. SIPLUS variants) (All versions), SIMATIC S7-400 PN/DP V7 CPU family (incl. SIPLUS variants) (All versions), SIMATIC S7-400 V6 and earlier CPU family (All versions), SIMATIC S7-400 V7 CPU family (All versions). Specially crafted packets sent to port 80/tcp could cause the affected devices to go into defect mode. A cold restart is required to recover the system.

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

Denial of service vulnerability in Siemens SIMATIC S7-300 and S7-400 PLCs where specially crafted TCP packets sent to port 80 cause the CPU to enter a defect mode, requiring a cold restart to recover. The attack requires network access to the PLC's web interface port.

MitigationIsolate affected PLCs behind firewalls or air-gapped networks, block port 80/tcp at network perimeter, and implement monitoring for anomalous traffic to port 80 on industrial network segments.

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
Simatic S7 300 Cpu FirmwareOperating system
Affected:all versions
Simatic S7 400 Cpu FirmwareOperating system
Affected:all versions

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
None
Integrity
None
Availability
High

CVSS:3.1/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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify Siemens S7-300 or S7-400 PLCs on your network
    Inventory your industrial network assets and identify any PLCs with product names matching 'SIMATIC S7-300' or 'SIMATIC S7-400'. Check your asset management system, network scans (using tools like nmap or industrial protocol scanners), or consult with your OT engineering team.
    Affected if You have any SIMATIC S7-300 or S7-400 CPU devices deployed in your environment.
  2. Verify if port 80 is open on the PLCs
    Perform a port scan targeting the IP addresses of identified S7-300/S7-400 PLCs specifically checking TCP port 80. Use nmap with command: nmap -p 80 <target_ip> or your network monitoring tool to check for port 80 listeners.
    Affected if Port 80/tcp is open and responding on any S7-300 or S7-400 PLC.
  3. Confirm the web server feature is enabled on the PLC
    Access the PLC's web-based management interface via HTTP on port 80 (e.g., http://<plc_ip_address>) using a standard web browser. Log in with appropriate credentials if required. Alternatively, check the PLC configuration in TIA Portal or Step 7 for web server module settings.
    Affected if The web interface is accessible and responds to HTTP requests on port 80.
  4. Assess network accessibility of port 80
    Review firewall rules, network segmentation, and ACLs to determine whether port 80 on the PLCs can be reached from network segments outside the OT/ICS zone, including corporate networks or the internet. Trace the network path and test reachability from an unauthorized endpoint if permitted.
    Affected if Port 80 on the PLC is reachable from any network segment less trusted than the PLC's dedicated control system network.
  5. Check PLC operational status for defect mode indicators
    Observe the PLC CPU status LEDs (SF/STOP LED pattern) and verify if the PLC has entered a defect/fault state requiring cold restart. Query the PLC via Step 7 or TIA Portal diagnostics, or check with your HMI/SCADA system for unexpected PLC fault alarms.
    Affected if The PLC displays a defect mode status or requires a cold restart to recover normal operation.

You are affected if you have any S7-300 or S7-400 PLCs with the web interface (port 80/tcp) enabled and accessible from your network, particularly from segments outside the control system zone.

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.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Isolate affected PLCs behind firewalls or air-gapped networks, block port 80/tcp at network perimeter, and implement monitoring for anomalous traffic to port 80 on industrial network segments.

Fix this in Simatic S7 300 Cpu 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-2016-9158 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