dbcve.org
Simatic S7 300 FirmwareOperating system · Siemens

CVE-2018-16561

HIGH · 7.5 CVSS v3.1 Published 2019-04-17
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 CPUs (All versions < V3.X.16). The affected CPUs improperly validate S7 communication packets which could cause a Denial-of-Service condition of the CPU. The CPU will remain in DEFECT mode until manual restart. Successful exploitation requires an attacker to be able to send a specially crafted S7 communication packet to a communication interface of the CPU. This includes Ethernet, PROFIBUS, and Multi Point Interfaces (MPI). No user interaction or privileges are required to exploit the security vulnerability. The vulnerability could allow causing a Denial-of-Service condition of the core functionality of the CPU, compromising the availability of the system. At the time of advisory publication no public exploitation of this security vulnerability was known. Siemens confirms the security vulnerability and provides mitigations to resolve the security issue.

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

The SIMATIC S7-300 CPUs contain an input validation vulnerability in the S7 communication protocol handler. Specially crafted S7 packets sent to Ethernet, PROFIBUS, or MPI interfaces cause the CPU to enter DEFECT mode, requiring manual restart to recover. This is a denial-of-service vulnerability with no authentication required.

MitigationUpdate all affected S7-300 CPUs to firmware version V3.X.16 or later. For systems where immediate updates are not feasible, implement network segmentation and access controls to limit exposure of the industrial communication interfaces to untrusted networks.

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 FirmwareOperating system
Affected:all versions
Simatic S7 300f FirmwareOperating system
Affected:all versions
Simatic S7 300fs FirmwareOperating system
Affected:all versions
Simatic S7 300t 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 the device model
    Check the CPU type marking on the physical hardware or in the TIA Portal project properties. Look for model numbers matching S7-300, S7-300f, S7-300fs, or S7-300t.
    Affected if The device is any SIMATIC S7-300 series CPU (standard, f, fs, or t variants).
  2. Determine the firmware version
    In TIA Portal, go to the device properties and view the firmware version. Alternatively, use the PLC navigation in TIA Portal or access the device via SIMATIC Manager to read the firmware version from the CPU module information.
    Affected if The firmware version is any version below V3.X.16 (all versions prior to the fix are affected).
  3. Check if S7 communication is enabled on Ethernet
    In TIA Portal, open the device configuration and expand the CPU properties. Under 'Protection & Security' or 'Communication', verify if Ethernet/PROFINET interfaces have S7 communication enabled. Also check if the PLC has assigned Ethernet nodes.
    Affected if The Ethernet interface is configured and S7 communication is active on TCP/102 (S7comm).
  4. Check PROFIBUS and MPI interface configuration
    In TIA Portal or SIMATIC Manager, verify if PROFIBUS or MPI interfaces are configured in the hardware configuration. Check the interface parameters and ensure they are not disabled.
    Affected if PROFIBUS or MPI interfaces are configured and active (even if not actively communicating).
  5. Assess network exposure of industrial interfaces
    Review network diagrams and firewall rules to determine if the Ethernet (TCP/102), PROFIBUS, or MPI interfaces are accessible from untrusted or external networks. Use port scanning (nmap -sV target -p 102) to verify if port 102 is exposed.
    Affected if The S7 communication interfaces (Ethernet port 102, PROFIBUS, or MPI) are reachable from untrusted network segments.

The environment is affected if any SIMATIC S7-300, S7-300f, S7-300fs, or S7-300t CPU with firmware below V3.X.16 has its S7 communication interfaces (Ethernet, PROFIBUS, or MPI) enabled and exposed to the network where the crafted packets could be received.

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

Update all affected S7-300 CPUs to firmware version V3.X.16 or later. For systems where immediate updates are not feasible, implement network segmentation and access controls to limit exposure of the industrial communication interfaces to untrusted networks.

Fix this in Simatic S7 300 Firmware Scoped from the published advisory
  • Consultation8.0 h
  • Implementation16.0 h
  • Testing12.0 h
  • Review / QA4.0 h
40.0 hours of engineering $7,000
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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-2018-16561 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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  • No spam, self-promotion, credentials, or personal data