CVE-2021-37206Network attack vector

Remote restart via malformed Ethernet packets

Published Sep 14, 2021 · Updated Aug 4, 2024

Improper input validation in Siemens SIPROTEC 5 relays before 8.80 allows remote attackers to restart devices via crafted Ethernet packets. The network packet-processing path fails to validate specially crafted web packets before processing them. Access to any device Ethernet interface is sufficient, and successful exploitation interrupts service by forcing the relay to restart.

CVSS severity7.5
High
EPSS probability1.43%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in Siemens SIPROTEC 5 relays before 8.80 allows remote attackers to restart devices via crafted Ethernet packets. The network packet-processing path fails to validate specially crafted web packets before processing them. Access to any device Ethernet interface is sufficient, and successful exploitation interrupts service by forcing the relay to restart.

The record

CVE
CVE-2021-37206
Published
Sep 14, 2021
Updated
Aug 4, 2024
Vendor
Siemens
Product
SIPROTEC 5 relays with CPU variant CP100
Classifications
CWE-20, T0814
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 14, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record 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 < V8.80

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Siemens · SIPROTEC 5 relays with CPU variant CP100version=All versions < V8.80
Siemens · SIPROTEC 5 relays with CPU variant CP050version=All versions < V8.80
Siemens · SIPROTEC 5 relays with CPU variant CP300version=All versions < V8.80

Published CVSS scores

7.5NVDCVSS: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-20Improper Input Validation
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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