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Simatic S7 PlcsimApplication · Siemens

CVE-2021-25673

MEDIUM · 5.5 CVSS v3.1 Published 2021-03-15
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
57/100
Remediation priority · Elevated
Zero-click

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 · unedited
A vulnerability has been identified in SIMATIC S7-PLCSIM V5.4 (All versions). An attacker with local access to the system could cause a Denial-of-Service condition in the application when it is used to open a specially crafted file. As a consequence, the application could enter an infinite loop, become unresponsive and must be restarted to restore the service.

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 · high confidence

A denial-of-service vulnerability exists in SIMATIC S7-PLCSIM V5.4 where opening a specially crafted file causes the application to enter an infinite loop, making it unresponsive until manually restarted.

MitigationApply the vendor patch from Siemens when available. Until then, restrict local access to the system and avoid opening files from untrusted sources.

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 data
Simatic S7 PlcsimApplication
Affected:all versions

CVSS 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
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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 checks

Work through these to decide whether this CVE applies to you.

  1. Verify SIMATIC S7-PLCSIM installation
    Search the system for Siemens Simatic S7-PLCSIM software using system inventory tools or check standard program installation directories
    Affected if The software is present on the system
  2. Identify installed version
    Locate and open the software's About or Help section, or check the installed programs list in the system control panel
    Affected if Any version of SIMATIC S7-PLCSIM is found installed
  3. Confirm vulnerability scope
    Compare your installed version against the affected range
    Affected if The installed version falls within all versions of SIMATIC S7-PLCSIM (the CVE affects all versions)
  4. Assess file handling exposure
    Review whether users on the system have the ability to open external or untrusted project files within the application
    Affected if Users can open files from untrusted sources into the SIMATIC S7-PLCSIM environment

The environment is affected if Siemens Simatic S7-PLCSIM software is installed, regardless of version, and users can open project or configuration files within the application.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply the vendor patch from Siemens when available. Until then, restrict local access to the system and avoid opening files from untrusted sources.

Fix this in Simatic S7 Plcsim Scoped from the published advisory
  • Consultation2.0 h
  • Implementation1.0 h
  • Testing4.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,360
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-25673 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • 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
  • No spam, self-promotion, credentials, or personal data