CVE-2021-37204Network attack vector

Unauthenticated service interruption via crafted port 102 packet

Published Feb 9, 2022 · Updated Apr 18, 2025

Denial of service in Siemens SIMATIC PLC products allows remote attackers to interrupt operation with a crafted packet on TCP port 102. The affected firmware operates on a resource after it has expired or been released while handling the packet; Siemens has not disclosed the resource or code path. No authentication or user interaction is required, and recovery requires restarting the affected PLC or simulated controller.

CVSS severity7.5
High
EPSS probability2.18%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Siemens SIMATIC PLC products allows remote attackers to interrupt operation with a crafted packet on TCP port 102. The affected firmware operates on a resource after it has expired or been released while handling the packet; Siemens has not disclosed the resource or code path. No authentication or user interaction is required, and recovery requires restarting the affected PLC or simulated controller.

The record

CVE
CVE-2021-37204
Published
Feb 9, 2022
Updated
Apr 18, 2025
Vendor
Siemens
Product
SIMATIC ET 200SP Open Controller CPU 1515SP PC2 Ready4Linux
Classifications
CWE-672, T0814, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 9, 2022CVE publishedPublication date reported by the CVE source.
  2. Apr 18, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

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 ET 200SP Open Controller CPU 1515SP PC2 Ready4Linuxversion=All versions
Siemens · SIMATIC S7-1500 CPUversion=All versions < V2.9.2; version=All versions >= V2.9.2 < V2.9.4
Siemens · SIMATIC ET 200SP Open Controller CPU 1515SP PC2version=All versions < V21.9; version=All versions >= V21.9 < V21.9.4
Siemens · TIM 1531 IRCversion=All versions < V2.3.6
Siemens · SIMATIC S7-PLCSIM Advancedversion=All versions < V4.0; version=All versions >= V4.0 < V4.0 SP1
Siemens · SIMATIC S7-1500 Software Controllerversion=All versions < V21.9; version=All versions >= V21.9 < V21.9.4
Siemens · SIMATIC ET 200SP Open Controller CPU 1515SP PCversion=All versions
Siemens · SIPLUS TIM 1531 IRCversion=All versions < V2.3.6
Siemens · SIMATIC S7-1200 CPUversion=All versions < V4.5.0; version=All versions >= V4.5.0 < V4.5.2
Siemens · SIMATIC Drive Controllerversion=All versions < V2.9.2; version=All versions >= V2.9.2 < V2.9.4

Published CVSS scores

7.5Siemens ProductCERTCVSS: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-672Operation on a Resource after Expiration or Release
T0814Denial of Service
T1499Endpoint Denial 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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