CVE-2021-27388Network attack vector

Unauthenticated configuration changes and control commands

Published Jun 15, 2021 · Updated Aug 3, 2024

Improper input validation in all versions of Siemens SINAMICS SL150, SM150, and SM150i allows remote attackers to issue limited control commands. Siemens has not disclosed the exact input or validation failure in the Sm@rtServer component; crafted remote traffic can also change limited configuration settings or interrupt service. Exploitation requires Sm@rtServer to be enabled, which is not the default, and network access to its TCP port 5900 service.

CVSS severity9.8
Critical
EPSS probability1.54%
Next 30 days · Sep 17, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in all versions of Siemens SINAMICS SL150, SM150, and SM150i allows remote attackers to issue limited control commands. Siemens has not disclosed the exact input or validation failure in the Sm@rtServer component; crafted remote traffic can also change limited configuration settings or interrupt service. Exploitation requires Sm@rtServer to be enabled, which is not the default, and network access to its TCP port 5900 service.

The record

CVE
CVE-2021-27388
Published
Jun 15, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-20, T0814, T0855
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 15, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
7.5NIST NVDAV:N/AC:L/Au:N/C:P/I:P/A:P

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
T0855Unauthorized Command Message

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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