CVE-2021-44695Network attack vector

Device denial of service via malformed TCP packets

Published Dec 13, 2022 · Updated Apr 21, 2025

Improper syntax validation in Siemens SIMATIC controllers allows remote authenticated users to interrupt devices through TCP port 102. The affected firmware processes specially crafted packets without correctly validating their syntax on the S7 communications service. High-privilege service access is required, and successful exploitation causes device denial of service.

CVSS severity4.9
Medium
EPSS probability0.72%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper syntax validation in Siemens SIMATIC controllers allows remote authenticated users to interrupt devices through TCP port 102. The affected firmware processes specially crafted packets without correctly validating their syntax on the S7 communications service. High-privilege service access is required, and successful exploitation causes device denial of service.

The record

CVE
CVE-2021-44695
Published
Dec 13, 2022
Updated
Apr 21, 2025
Vendor
Siemens
Product
SIMATIC S7-1500 CPU 1518T-4 PN/DP
Classifications
CWE-1286, T1499
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Dec 13, 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

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 < V3.0.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

Siemens · SIMATIC S7-1500 CPU 1518T-4 PN/DPversion=All versions < V3.0.1
Siemens · SIMATIC S7-1500 CPU 1512SP-1 PNversion=All versions < V2.9.7
Siemens · SIMATIC S7-1500 CPU 1515T-2 PNversion=All versions < V2.9.7
Siemens · SIMATIC S7-1500 ET 200pro: CPU 1516PRO F-2 PNversion=All versions < V2.9.7
Siemens · SIPLUS ET 200SP CPU 1510SP-1 PN RAILversion=All versions < V2.9.7
Siemens · SIPLUS ET 200SP CPU 1510SP F-1 PN RAILversion=All versions < V2.9.7
Siemens · SIMATIC S7-1500 CPU 1517F-3 PN/DPversion=All versions < V3.0.1
Siemens · SIMATIC S7-1500 ET 200pro: CPU 1513PRO F-2 PNversion=All versions < V2.9.7
Siemens · SIMATIC S7-1500 CPU S7-1518-4 PN/DP ODKversion=All versions < V2.9.7
Siemens · SIMATIC S7-1500 CPU 1517TF-3 PN/DPversion=All versions < V3.0.1
Siemens · SIPLUS S7-1500 CPU 1516F-3 PN/DP RAILversion=All versions < V2.9.7
Siemens · SIMATIC S7-1500 Software Controller V2version=All versions < V21.9.7
Siemens · SIPLUS S7-1500 CPU 1518-4 PN/DP MFPversion=All versions < V3.0.1
Siemens · SIMATIC S7-1500 CPU 1516-3 PN/DPversion=All versions < V2.9.7
Siemens · SIPLUS S7-1500 CPU 1516-3 PN/DP RAILversion=All versions < V2.9.7
Siemens · SIMATIC S7-1500 CPU 1518TF-4 PN/DPversion=All versions < V3.0.1
Siemens · SIMATIC S7-1500 CPU 1517H-3 PNversion=All versions < V3.0.1
Siemens · SIPLUS ET 200SP CPU 1510SP F-1 PNversion=All versions < V2.9.7
Siemens · SIMATIC ET 200SP Open Controller CPU 1515SP PC2version=All versions < V21.9.7
Siemens · SIMATIC S7-1500 CPU 1512SP F-1 PNversion=All versions < V2.9.7
Siemens · SIMATIC S7-1500 CPU 1511F-1 PNversion=All versions < V2.9.7
Siemens · SIPLUS S7-1500 CPU 1518F-4 PN/DPversion=All versions < V3.0.1
Siemens · SIPLUS S7-1500 CPU 1518HF-4 PNversion=All versions < V3.0.1
Siemens · SIMATIC S7-1500 CPU 1511TF-1 PNversion=All versions < V2.9.7
Siemens · SIPLUS ET 200SP CPU 1512SP F-1 PN RAILversion=All versions < V2.9.7
Siemens · TIM 1531 IRCversion=All versions < V2.3.6
Siemens · SIMATIC S7-1500 CPU 1513-1 PNversion=All versions < V2.9.7
Siemens · SIMATIC Drive Controller CPU 1507D TFversion=All versions < V2.9.7
Siemens · SIMATIC S7-1500 CPU 1516F-3 PN/DPversion=All versions < V2.9.7
Siemens · SIMATIC S7-1500 ET 200pro: CPU 1513PRO-2 PNversion=All versions < V2.9.7
Siemens · SIMATIC S7-1500 CPU S7-1518F-4 PN/DP ODKversion=All versions < V2.9.7
Siemens · SIMATIC S7-1500 CPU 1511T-1 PNversion=All versions < V2.9.7
Siemens · SIMATIC S7-1500 CPU 1518F-4 PN/DP MFPversion=All versions < V3.0.1
Siemens · SIPLUS S7-1500 CPU 1511-1 PN T1 RAILversion=All versions < V2.9.7
Siemens · SIMATIC S7-1500 CPU 1511-1 PNversion=All versions < V2.9.7
Siemens · SIPLUS S7-1500 CPU 1511F-1 PNversion=All versions < V2.9.7
Siemens · SIPLUS ET 200SP CPU 1512SP-1 PNversion=All versions < V2.9.7
Siemens · SIMATIC S7-PLCSIM Advancedversion=All versions < V5.0
Siemens · SIPLUS S7-1500 CPU 1511-1 PN TX RAILversion=All versions < V2.9.7
Siemens · SIPLUS S7-1500 CPU 1515F-2 PNversion=All versions < V2.9.7
Siemens · SIPLUS S7-1500 CPU 1518-4 PN/DPversion=All versions < V3.0.1
Siemens · SIMATIC S7-1500 CPU 1513F-1 PNversion=All versions < V2.9.7
Siemens · SIMATIC S7-1500 CPU 1516T-3 PN/DPversion=All versions < V3.0.1
Siemens · SIPLUS S7-1500 CPU 1517H-3 PNversion=All versions < V3.0.1
Siemens · SIPLUS S7-1500 CPU 1513-1 PNversion=All versions < V2.9.7
Siemens · SIPLUS S7-1500 CPU 1516F-3 PN/DPversion=All versions < V2.9.7
Siemens · SIPLUS S7-1500 CPU 1513F-1 PNversion=All versions < V2.9.7
Siemens · SIPLUS TIM 1531 IRCversion=All versions < V2.3.6
Siemens · SIPLUS S7-1500 CPU 1516-3 PN/DPversion=All versions < V2.9.7
Siemens · SIMATIC S7-1500 CPU 1518F-4 PN/DPversion=All versions < V3.0.1
Siemens · SIMATIC S7-1500 CPU 1512C-1 PNversion=All versions < V2.9.7
Siemens · SIMATIC S7-1500 CPU 1513R-1 PNversion=All versions < V2.9.7
Siemens · SIPLUS S7-1500 CPU 1511-1 PNversion=All versions < V2.9.7
Siemens · SIMATIC S7-1500 CPU 1518HF-4 PNversion=All versions < V3.0.1
Siemens · SIMATIC S7-1200 CPUversion=All versions < V4.6.0
Siemens · SIMATIC S7-1500 CPU 1515F-2 PNversion=All versions < V2.9.7
Siemens · SIMATIC S7-1500 CPU 1518-4 PN/DPversion=All versions < V3.0.1
Siemens · SIPLUS ET 200SP CPU 1512SP-1 PN RAILversion=All versions < V2.9.7
Siemens · SIMATIC Drive Controller CPU 1504D TFversion=All versions < V2.9.7
Siemens · SIPLUS S7-1500 CPU 1516-3 PN/DP TX RAILversion=All versions < V2.9.7
Siemens · SIPLUS ET 200SP CPU 1510SP-1 PNversion=All versions < V2.9.7
Siemens · SIMATIC S7-1500 CPU 1517T-3 PN/DPversion=All versions < V3.0.1
Siemens · SIMATIC S7-1500 CPU 1511C-1 PNversion=All versions < V2.9.7
Siemens · SIMATIC S7-1500 CPU 1510SP-1 PNversion=All versions < V2.9.7
Siemens · SIMATIC S7-1500 CPU 1515-2 PNversion=All versions < V2.9.7
Siemens · SIPLUS S7-1500 CPU 1515F-2 PN RAILversion=All versions < V2.9.7
Siemens · SIMATIC S7-1500 CPU 1518-4 PN/DP MFPversion=All versions < V3.0.1
Siemens · SIMATIC S7-1500 CPU 1515R-2 PNversion=All versions < V2.9.7
Siemens · SIPLUS S7-1500 CPU 1515R-2 PN TX RAILversion=All versions < V2.9.7
Siemens · SIPLUS S7-1500 CPU 1515F-2 PN T2 RAILversion=All versions < V2.9.7
Siemens · SIPLUS S7-1500 CPU 1515R-2 PNversion=All versions < V2.9.7
Siemens · SIMATIC S7-1500 CPU 1515TF-2 PNversion=All versions < V2.9.7
Siemens · SIMATIC S7-1500 CPU 1516TF-3 PN/DPversion=All versions < V3.0.1
Siemens · SIMATIC S7-1500 ET 200pro: CPU 1516PRO-2 PNversion=All versions < V2.9.7
Siemens · SIMATIC S7-1500 CPU 1517-3 PN/DPversion=All versions < V3.0.1
Siemens · SIPLUS ET 200SP CPU 1512SP F-1 PNversion=All versions < V2.9.7
Siemens · SIMATIC S7-1500 CPU 1510SP F-1 PNversion=All versions < V2.9.7

Published CVSS scores

4.9Siemens ProductCERTCVSS:3.1/AV:N/AC:L/PR:H/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
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-1286Improper Validation of Syntactic Correctness of Input
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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