CVE-2021-27395Network attack vector

Unauthenticated data manipulation via critical interface

Published Oct 12, 2021 · Updated Aug 3, 2024

Missing authentication in Siemens SIMATIC Process Historian 2014 before SP3 Update 6 allows remote attackers to alter archived data. A critical-function interface accepts requests without authentication and permits insertion, modification, or deletion of historian records. The interface is reachable over the network; successful requests can compromise data integrity and interrupt historian availability, but no confidentiality impact is reported.

CVSS severity8.1
High
EPSS probability0.80%
Next 30 days · Sep 17, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Missing authentication in Siemens SIMATIC Process Historian 2014 before SP3 Update 6 allows remote attackers to alter archived data. A critical-function interface accepts requests without authentication and permits insertion, modification, or deletion of historian records. The interface is reachable over the network; successful requests can compromise data integrity and interrupt historian availability, but no confidentiality impact is reported.

The record

CVE
CVE-2021-27395
Published
Oct 12, 2021
Updated
Aug 3, 2024
Vendor
Siemens
Product
SIMATIC Process Historian
Classifications
CWE-306, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 12, 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?

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

  1. Affected versionversion=All versions
  2. Affected versionversion=All versions < SP3 Update 6

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Siemens · SIMATIC Process Historianversion=All versions; version=All versions < SP3 Update 6

Published CVSS scores

5.5NVDAV:N/AC:L/Au:S/C:N/I:P/A:P
8.1NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/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-306Missing Authentication for Critical Function
T1190Exploit Public-Facing Application

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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