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Capital VstarApplication · Siemens

CVE-2021-31883

HIGH · 7.5 CVSS v3.1 Published 2021-11-09
Fix available
A fix is available. Upgrade to 2017.02.1 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
A vulnerability has been identified in Capital Embedded AR Classic 431-422 (All versions), Capital Embedded AR Classic R20-11 (All versions < V2303). When processing a DHCP ACK message, the DHCP client application does not validate the length of the Vendor option(s), leading to Denial-of-Service conditions. (FSMD-2021-0013)

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 DHCP client in Capital Embedded AR Classic fails to validate the length of Vendor options when processing DHCP ACK messages. This missing bounds check allows malformed packets to cause a denial-of-service condition by triggering the vulnerability during DHCP negotiation.

MitigationUpgrade Capital Embedded AR Classic to V2303 or later, which contains the vendor option length validation fix.

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
Capital VstarApplication
Affected:all versions
Nucleus NetApplication
Affected:all versions
Nucleus Readystart V3Application
Affected:< 2017.02.1
Nucleus Source CodeApplication
Affected:all versions
Apogee Modular Building Controller FirmwareOperating system
Affected:all versions
Apogee Modular Equiment Controller FirmwareOperating system
Affected:all versions
Apogee Pxc Compact FirmwareOperating system
Affected:all versions
Apogee Pxc Modular FirmwareOperating system
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
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/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. Identify the deployed product and version
    Query the system firmware, software inventory, or bootloader to determine which Siemens product is in use (Capital Vstar, Nucleus Net, Nucleus Readystart V3, Nucleus Source Code, or one of the Apogee controller firmwares). Record the exact version string.
    Affected if The product is any version of Capital Vstar, Nucleus Net, Nucleus Source Code, or Apogee firmwares (all versions affected), or Nucleus Readystart V3 with version prior to 2017.02.1
  2. Confirm DHCP client functionality is enabled
    Inspect the system configuration, build settings, or runtime environment to determine whether the DHCP client service is active. This may involve checking network configuration files, process lists, or embedded system initialization scripts.
    Affected if DHCP client is enabled and the system performs DHCP negotiation (DHCP ACK messages are processed)
  3. Verify the DHCP client component version
    If the product includes the Capital Embedded AR Classic components as a separate module, check the associated libraries or firmware metadata for the DHCP client version. Compare against the fixed version V2303 mentioned in the vendor advisory.
    Affected if The DHCP client component version is earlier than V2303, or for Nucleus Readystart V3, earlier than 2017.02.1
  4. Review DHCP packet processing configuration
    Examine network interface settings or DHCP configuration to confirm the system is configured to receive and process DHCP ACK messages from a DHCP server.
    Affected if The system is configured to obtain IP addresses via DHCP (the vulnerability triggers during DHCP ACK message processing)

A user is affected if their deployed Siemens product uses the Capital Embedded AR Classic DHCP client with a version earlier than V2303 (or Nucleus Readystart V3 earlier than 2017.02.1) and has DHCP client functionality enabled for network configuration.

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 2017.02.1 or later
Fixed in 2017.02.1
Interim mitigation

Upgrade Capital Embedded AR Classic to V2303 or later, which contains the vendor option length validation fix.

Fix this in Capital Vstar Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing16.0 h
  • Review / QA4.0 h
32.0 hours of engineering $5,360
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $8,576.

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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-2021-31883 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