CVE-2021-25674
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 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, a NULL pointer deference condition could cause the application to terminate unexpectedly 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 · moderate confidenceA NULL pointer dereference vulnerability exists in SIMATIC S7-PLCSIM V5.4 where opening a specially crafted file causes the application to crash. An attacker with local access can trigger this DoS condition, requiring manual restart of the service.
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= 5.4CVSS 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 checksWork through these to decide whether this CVE applies to you.
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Verify SIMATIC S7-PLCSIM is installedCheck for the presence of the application in the system registry (HKLM\SOFTWARE\Siemens\S7-PLCSIM) or look in typical installation directories such as C:\Program Files\Siemens\PLCSIM or C:\Program Files (x86)\Siemens\PLCSIMAffected if SIMATIC S7-PLCSIM is installed on the system
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Confirm installed version is 5.4Open Windows Control Panel > Programs and Features, find SIMATIC S7-PLCSIM, and verify the version column shows exactly 5.4, or right-click the executable (typically S7PCHS.exe or PLCSIM.exe) in the installation folder, select Properties, and check the File VersionAffected if The installed version is exactly 5.4
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Check if file import/open functionality is accessibleLaunch SIMATIC S7-PLCSIM and verify the application allows opening or importing project files, backup files, or similar file types (typically via File menu options such as Open, Import, or Load)Affected if The file opening/import feature is present and accessible to local users
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Verify local user access to the applicationConfirm that untrusted local users could potentially introduce specially crafted files to the system and trigger the file opening operation - check file system permissions on common user-accessible directories and the application's execution permissionsAffected if Local users without elevated privileges can access and run the application and introduce files to the environment
A system is affected if SIMATIC S7-PLCSIM version 5.4 is installed and local users can open project or import files within the application.
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.
From vendor dataAvoid opening untrusted or unverified files with SIMATIC S7-PLCSIM. Implement proper file parsing validation and error handling to prevent NULL pointer dereferences. Monitor for vendor patches.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA4.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $6,176.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-25674 — 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-2021-25674 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
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