CVE-2021-27395
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedA vulnerability has been identified in SIMATIC Process Historian 2013 and earlier (All versions), SIMATIC Process Historian 2014 (All versions < SP3 Update 6), SIMATIC Process Historian 2019 (All versions), SIMATIC Process Historian 2020 (All versions). An interface in the software that is used for critical functionalities lacks authentication, which could allow a malicious user to maliciously insert, modify or delete data.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · moderate confidenceSIMATIC Process Historian versions 2013 and earlier, 2014 (pre-SP3 Update 6), 2019, and 2020 contain an unauthenticated interface used for critical functionalities. This allows remote attackers to insert, modify, or delete data without credentials due to missing authentication checks on a specific interface.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE dataall versionsall versionsall versionsall versionsCVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify installed Process Historian versionCheck the program version through Windows Programs and Features, or look in the installation directory for version information files. Compare against affected versions: 2013 (all), 2014 (all before SP3 Update 6), 2019 (all), 2020 (all).Affected if Version matches one of the affected releases listed in the CVE.
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Locate the Process Historian installation pathFind the main installation directory, typically under C:\Program Files\Siemens\Process Historian or similar Siemens installation paths. Identify the web server or service components that expose the interface.Affected if The application is installed and exposes network services.
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Determine network exposure of the vulnerable interfaceReview firewall rules and network configuration to determine if the Process Historian web interface or API ports (commonly HTTP/HTTPS ports used by the application) are accessible from untrusted networks or the internet.Affected if The interface is reachable from networks outside the trusted environment without authentication barriers.
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Test interface for missing authenticationIf you can safely access the application, attempt to reach the critical data insertion/modification interface without providing any credentials. Observe whether the request succeeds or returns protected data without authentication challenges.Affected if The interface returns successful responses or allows data operations without requiring authentication.
You are affected if you have SIMATIC Process Historian version 2013, 2014 (pre-SP3 Update 6), 2019, or 2020 installed and the vulnerable interface is network-accessible without authentication.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scopedImplement authentication requirements on the vulnerable interface. Restrict network access to critical Process Historian services and validate all input through authorized channels only.
Simatic Process Historian 2014 SP3 Update 6 or later (for 2019/2020, obtain patch from Siemens)
- 1. Identify the current installed version of Simatic Process Historian via the Siemens Industry Online Support (SIOS) portal or system documentation
- 2. For Simatic Process Historian 2014: Upgrade to SP3 Update 6 or later, as versions prior to SP3 Update 6 are vulnerable
- 3. For Simatic Process Historian 2019 and 2020: Contact Siemens customer support to obtain the appropriate patch or planned update that addresses CVE-2021-27395
- 4. After upgrading, verify that authentication is now required for the previously unauthenticated interface
- 5. Test critical functionalities to ensure the system operates correctly post-patch
- 6. Review Siemens security advisory for any additional required actions or configuration changes
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation6.0 h
- Implementation12.0 h
- Testing8.0 h
- Review / QA4.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-27395 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-27395 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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