dbcve.org
Simatic Mv420 FirmwareOperating system · Siemens

CVE-2020-27632

HIGH · 7.5 CVSS v3.1 Published 2021-03-10
Fix available
A fix is available. Upgrade to 7.0.6 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges 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
In SIMATIC MV400 family versions prior to v7.0.6, the ISN generator is initialized with a constant value and has constant increments. An attacker could predict and hijack TCP sessions.

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 SIMATIC MV400 family devices use a weak ISN (Initial Sequence Number) generator initialized with a constant value and constant increments. This predictable sequence allows remote attackers to calculate future ISN values and inject or hijack TCP sessions.

MitigationUpdate SIMATIC MV400 devices to firmware version 7.0.6 or later, which implements randomized ISN generation. Apply within a planned maintenance window given industrial environment constraints.

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 Mv420 FirmwareOperating system
Affected:< 7.0.6
Simatic Mv440 FirmwareOperating system
Affected:< 7.0.6

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

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

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 the SIMATIC MV model
    Access the device web interface or check the device label to confirm whether it is an MV420 or MV440 model.
    Affected if The device is a Siemens SIMATIC MV420 or MV440 unit.
  2. Determine the current firmware version
    Log into the device web interface and navigate to the 'Device Information' or 'Overview' page to view the installed firmware version. Alternatively, use the device's diagnostic interface or management console to query the firmware version.
    Affected if The device model is confirmed as MV420 or MV440.
  3. Compare firmware version to affected range
    Check if the installed firmware version is less than 7.0.6. Note the exact version number displayed (for example, 7.0.5, 7.0.4, or earlier).
    Affected if The firmware version is below 7.0.6 (for example, 7.0.5, 7.0.3, or 6.x.x).

The device is affected if it is a SIMATIC MV420 or MV440 running firmware version earlier than 7.0.6, because the weak ISN generation vulnerability exists in those versions.

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
Upgrade available Upgrade to 7.0.6 or later
Fixed in 7.0.6
Interim mitigation

Update SIMATIC MV400 devices to firmware version 7.0.6 or later, which implements randomized ISN generation. Apply within a planned maintenance window given industrial environment constraints.

Fix this in Simatic Mv420 Firmware Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,860
Get the upgrade done

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 locally
dbcve dependency scanner

Check whether your project pulls in CVE-2020-27632 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

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-2020-27632 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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