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Deserialization of Untrusted DataWeakness · CWE-502

CVE-2025-40759

HIGH · 7.8 CVSS v3.1 Published 2025-08-12
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
81/100
Remediation priority · High
No privileges

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 V17 (All versions), SIMATIC STEP 7 V17 (All versions < V17 Update 9), SIMATIC STEP 7 V18 (All versions), SIMATIC STEP 7 V19 (All versions < V19 Update 4), SIMATIC STEP 7 V20 (All versions < V20 Update 4), SIMATIC WinCC V17 (All versions < V17 Update 9), SIMATIC WinCC V18 (All versions), SIMATIC WinCC V19 (All versions < V19 Update 4), SIMATIC WinCC V20 (All versions < V20 Update 4), SIMOCODE ES V17 (All versions), SIMOCODE ES V18 (All versions), SIMOCODE ES V19 (All versions), SIMOCODE ES V20 (All versions), SIMOTION SCOUT TIA V5.4 (All versions), SIMOTION SCOUT TIA V5.5 (All versions), SIMOTION SCOUT TIA V5.6 (All versions < V5.6 SP1 HF7), SIMOTION SCOUT TIA V5.7 (All versions), SINAMICS Startdrive V17 (All versions), SINAMICS Startdrive V18 (All versions), SINAMICS Startdrive V19 (All versions), SINAMICS Startdrive V20 (All versions), SIRIUS Safety ES V17 (TIA Portal) (All versions), SIRIUS Safety ES V18 (TIA Portal) (All versions), SIRIUS Safety ES V19 (TIA Portal) (All versions), SIRIUS Safety ES V20 (TIA Portal) (All versions), SIRIUS Soft Starter ES V17 (TIA Portal) (All versions), SIRIUS Soft Starter ES V18 (TIA Portal) (All versions), SIRIUS Soft Starter ES V19 (TIA Portal) (All versions), SIRIUS Soft Starter ES V20 (TIA Portal) (All versions), TIA Portal Cloud V17 (All versions), TIA Portal Cloud V18 (All versions), TIA Portal Cloud V19 (All versions < V5.2.1.1), TIA Portal Cloud V20 (All versions < V5.2.2.2). Affected products do not properly sanitize stored security properties when parsing project files. This could allow an attacker to cause a type confusion and execute arbitrary code within the affected application.

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

The vulnerability exists in multiple Siemens TIA Portal products (STEP 7, WinCC, SIMOCODE, SIMOTION, SINAMICS, SIRIUS, and related tools) where stored security properties within project files are not properly sanitized during parsing. This improper input validation can be exploited to cause a type confusion condition, allowing an attacker to achieve arbitrary code execution within the context of the affected application.

MitigationApply the vendor-supplied updates: Update STEP 7 and WinCC to V17 Update 9 or later, V19 Update 4 or later, V20 Update 4 or later; update SIMOTION SCOUT TIA V5.6 to V5.6 SP1 HF7 or later; update TIA Portal Cloud to V5.2.1.1 (V19) or V5.2.2.2 (V20) or later. Avoid opening untrusted project files from unknown sources until patches are applied.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

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
None
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

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

  1. Identify installed Siemens TIA Portal components
    Check Windows Programs and Features (appwiz.cpl) or registry under HKLM\SOFTWARE\Siemens for entries containing STEP 7, WinCC, SIMOTION, or TIA Portal
    Affected if Any of the following products are installed: STEP 7, WinCC, SIMOTION SCOUT TIA, SIMOCODE, SINAMICS, SIRIUS, or TIA Portal Cloud
  2. Check STEP 7 version
    Open SIMATIC Manager or TIA Portal, go to Help > About, or check registry under HKLM\SOFTWARE\Siemens\TIA\Portal\Version for the installed version number
    Affected if Version is V17 before Update 9, V19 before Update 4, or V20 before Update 4
  3. Check WinCC version
    Open WinCC Explorer or check registry under HKLM\SOFTWARE\Siemens\WinCC\Version for the installed version number
    Affected if Version is V17 before Update 9, V19 before Update 4, or V20 before Update 4
  4. Check SIMOTION SCOUT TIA version
    Open SIMOTION SCOUT TIA and go to Help > About, or check registry under HKLM\SOFTWARE\Siemens\SIMOTION\Version for the installed version number
    Affected if Version is V5.6 before SP1 HF7
  5. Check TIA Portal Cloud version
    Check the installed TIA Portal Cloud client version through the application or installed programs list
    Affected if Version is V19 before V5.2.1.1 or V20 before V5.2.2.2

A system is affected if any of the installed TIA Portal components (STEP 7, WinCC, SIMOTION SCOUT TIA, or TIA Portal Cloud) have versions that fall within the vulnerable ranges listed.

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.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply the vendor-supplied updates: Update STEP 7 and WinCC to V17 Update 9 or later, V19 Update 4 or later, V20 Update 4 or later; update SIMOTION SCOUT TIA V5.6 to V5.6 SP1 HF7 or later; update TIA Portal Cloud to V5.2.1.1 (V19) or V5.2.2.2 (V20) or later. Avoid opening untrusted project files from unknown sources until patches are applied.

Recommended fix High confidence

Upgrade to the specified Update versions (V17 Update 9, V19 Update 4, V20 Update 4, V5.6 SP1 HF7, TIA Portal Cloud V5.2.1.1 or V5.2.2.2 depending on product line)

  1. 1. Identify the specific Siemens product(s) and version(s) in use from the affected list (SIMATIC STEP 7, WinCC, SIMOCODE ES, SINAMICS Startdrive, SIRIUS Safety ES, SIRIUS Soft Starter ES, SIMOTION SCOUT TIA, TIA Portal Cloud, or S7-PLCSIM).
  2. 2. For SIMATIC STEP 7 V17: upgrade to V17 Update 9 or later.
  3. 3. For SIMATIC STEP 7 V19: upgrade to V19 Update 4 or later.
  4. 4. For SIMATIC STEP 7 V20: upgrade to V20 Update 4 or later.
  5. 5. For SIMATIC WinCC V17: upgrade to V17 Update 9 or later.
  6. 6. For SIMATIC WinCC V19: upgrade to V19 Update 4 or later.
  7. 7. For SIMATIC WinCC V20: upgrade to V20 Update 4 or later.
  8. 8. For TIA Portal Cloud V19: upgrade to V5.2.1.1 or later.
Caveat Newer updates may introduce changes to project file formats or PLC program behavior; thoroughly test existing projects after upgrade

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing12.0 h
  • Review / QA4.0 h
28.0 hours of engineering $4,760
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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-2025-40759 in production — separate from our analysis above.

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