CVE-2021-40368Network attack vector

Controller outage via malformed TCP packets

Published Apr 12, 2022 · Updated Apr 21, 2025

Input validation in Siemens SIMATIC S7-400 and S7-410 CPU firmware allows remote attackers to cause a denial of service over TCP port 102. The firmware improperly handles specially crafted packets during memory-buffer operations on the TCP/102 service. No authentication or user interaction is required, and successful exploitation stops normal operation until the controller is restarted.

CVSS severity7.5
High
EPSS probability1.00%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Input validation in Siemens SIMATIC S7-400 and S7-410 CPU firmware allows remote attackers to cause a denial of service over TCP port 102. The firmware improperly handles specially crafted packets during memory-buffer operations on the TCP/102 service. No authentication or user interaction is required, and successful exploitation stops normal operation until the controller is restarted.

The record

CVE
CVE-2021-40368
Published
Apr 12, 2022
Updated
Apr 21, 2025
Vendor
Siemens
Product
SIMATIC S7-400 CPU 412-1 DP V7
Classifications
CWE-119, T0814
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 12, 2022CVE publishedPublication date reported by the CVE source.
  2. Apr 21, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=All versions

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Siemens · SIMATIC S7-400 CPU 412-1 DP V7version=All versions
Siemens · SIPLUS S7-400 CPU 417-4 V7version=All versions
Siemens · SIMATIC S7-400 H V6 CPU familyversion=All versions < V6.0.10
Siemens · SIMATIC S7-410 V8 CPU family (incl. SIPLUS variants)version=All versions < V8.2.3
Siemens · SIMATIC S7-400 CPU 416-3 DP V7version=All versions
Siemens · SIMATIC S7-400 CPU 412-2 PN/DP V7version=All versions < V7.0.3
Siemens · SIMATIC S7-400 CPU 412-2 DP V7version=All versions
Siemens · SIPLUS S7-400 CPU 416-3 V7version=All versions
Siemens · SIMATIC S7-400 CPU 416-3 PN/DP V7version=All versions < V7.0.3
Siemens · SIMATIC S7-400 CPU 416F-2 DP V7version=All versions
Siemens · SIMATIC S7-410 V10 CPU familyversion=All versions < V10.1
Siemens · SIMATIC S7-400 CPU 414-3 DP V7version=All versions
Siemens · SIMATIC S7-400 CPU 417-4 DP V7version=All versions
Siemens · SIPLUS S7-400 CPU 414-3 PN/DP V7version=All versions < V7.0.3
Siemens · SIMATIC S7-400 CPU 414-2 DP V7version=All versions
Siemens · SIMATIC S7-400 CPU 414-3 PN/DP V7version=All versions < V7.0.3
Siemens · SIMATIC S7-400 CPU 416F-3 PN/DP V7version=All versions < V7.0.3
Siemens · SIMATIC S7-400 CPU 414F-3 PN/DP V7version=All versions < V7.0.3
Siemens · SIMATIC S7-400 CPU 416-2 DP V7version=All versions
Siemens · SIPLUS S7-400 CPU 416-3 PN/DP V7version=All versions < V7.0.3

Published CVSS scores

7.5Siemens AGCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-119Improper Restriction of Operations within the Bounds of a Memory Buffer
T0814Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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