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Uncontrolled Resource ConsumptionWeakness · CWE-400

CVE-2025-40944

HIGH · 7.5 CVSS v3.1 Published 2026-01-13
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 ET 200AL IM 157-1 PN (6ES7157-1AB00-0AB0) (All versions), SIMATIC ET 200MP IM 155-5 PN HF (6ES7155-5AA00-0AC0) (All versions >= V4.2.0), SIMATIC ET 200SP IM 155-6 MF HF (6ES7155-6MU00-0CN0) (All versions), SIMATIC ET 200SP IM 155-6 PN HA (incl. SIPLUS variants) (All versions < V1.3), SIMATIC ET 200SP IM 155-6 PN R1 (6ES7155-6AU00-0HM0) (All versions < V6.0.1), SIMATIC ET 200SP IM 155-6 PN/2 HF (6ES7155-6AU01-0CN0) (All versions >= V4.2.0 < V4.2.5), SIMATIC ET 200SP IM 155-6 PN/3 HF (6ES7155-6AU30-0CN0) (All versions < V4.2.2), SIMATIC PN/MF Coupler (6ES7158-3MU10-0XA0) (All versions), SIMATIC PN/PN Coupler (6ES7158-3AD10-0XA0) (All versions < V6.0.0), SIPLUS ET 200MP IM 155-5 PN HF (6AG1155-5AA00-2AC0) (All versions >= V4.2.0), SIPLUS ET 200MP IM 155-5 PN HF (6AG1155-5AA00-7AC0) (All versions >= V4.2.0), SIPLUS ET 200MP IM 155-5 PN HF T1 RAIL (6AG2155-5AA00-1AC0) (All versions >= V4.2.0), SIPLUS ET 200SP IM 155-6 PN HF (6AG1155-6AU01-2CN0) (All versions >= V4.2.0 < V4.2.5), SIPLUS ET 200SP IM 155-6 PN HF (6AG1155-6AU01-7CN0) (All versions >= V4.2.0 < V4.2.5), SIPLUS ET 200SP IM 155-6 PN HF T1 RAIL (6AG2155-6AU01-1CN0) (All versions >= V4.2.0 < V4.2.5), SIPLUS ET 200SP IM 155-6 PN HF TX RAIL (6AG2155-6AU01-4CN0) (All versions >= V4.2.0 < V4.2.5), SIPLUS NET PN/PN Coupler (6AG2158-3AD10-4XA0) (All versions < V6.0.0). Affected devices do not properly handle S7 protocol session disconnect requests. When receiving a valid S7 protocol Disconnect Request (COTP DR TPDU) on TCP port 102, the devices enter an improper session state. This could allow an attacker to cause the device to become unresponsive, leading to a denial-of-service condition that requires a power cycle to restore normal operation.

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

Affected Siemens SIMATIC ET 200 devices (ET 200AL, ET 200MP, ET 200SP, PN/MF Coupler, PN/PN Coupler and SIPLUS variants) do not properly handle S7 protocol session disconnect requests. When receiving a valid S7 protocol Disconnect Request (COTP DR TPDU) on TCP port 102, the devices enter an improper session state, causing them to become unresponsive and requiring a power cycle to restore normal operation.

MitigationApply available vendor firmware updates. Until patches are available, implement network segmentation and firewall rules to restrict unauthorized access to TCP port 102, and monitor for signs of exploitation that may indicate attempted DoS conditions.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

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 ET 200 device inventory
    Locate all SIMATIC ET 200 devices on the network (ET 200AL, ET 200MP, ET 200SP, PN/MF Coupler, PN/PN Coupler, SIPLUS variants) by reviewing engineering software projects, network scans, or physical asset lists
    Affected if Any of the listed ET 200 model families are present in the environment
  2. Determine device firmware versions
    Access each device via TIA Portal, web server, or device labeling to retrieve the current firmware version; compare against any vendor-released version information for this CVE
    Affected if The installed firmware version falls within the vulnerable version range published by Siemens for this CVE
  3. Verify TCP port 102 accessibility
    Scan network segments for devices listening on TCP port 102 (S7 communication) using tools like nmap: nmap -p 102 <target>
    Affected if TCP port 102 is open and reachable on the ET 200 devices
  4. Assess network exposure of port 102
    Review firewall rules, VLAN configurations, and access control lists to determine if TCP port 102 is exposed to untrusted networks or external interfaces
    Affected if Port 102 is accessible from less-trusted network segments or the internet without proper filtering
  5. Check for device responsiveness anomalies
    If devices are suspected, verify normal operation by attempting S7 communication via TIA Portal or testing basic read/write requests to the device
    Affected if Devices fail to respond to S7 protocol queries or show unexpected unresponsiveness after any recent network events involving port 102

The environment is affected if any Siemens SIMATIC ET 200 devices (ET 200AL, ET 200MP, ET 200SP, PN/MF Coupler, PN/PN Coupler, or SIPLUS variants) with vulnerable firmware are reachable on TCP port 102.

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

Apply available vendor firmware updates. Until patches are available, implement network segmentation and firewall rules to restrict unauthorized access to TCP port 102, and monitor for signs of exploitation that may indicate attempted DoS conditions.

Have this fixed Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA2.0 h
20.0 hours of engineering $3,500
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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-2025-40944 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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