dbcve.org
Capital VstarApplication · Siemens

CVE-2021-31345

CRITICAL · 9.1 CVSS v3.1 Published 2021-11-09
Fix available
A fix is available. Upgrade to 2014.12 or later.
See remediation →
100/100
Remediation priority · Urgent
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), PLUSCONTROL 1st Gen (All versions). The total length of an UDP payload (set in the IP header) is unchecked. This may lead to various side effects, including Information Leak and Denial-of-Service conditions, depending on a user-defined applications that runs on top of the UDP protocol. (FSMD-2021-0006)

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 confidence

A length validation vulnerability exists in the UDP protocol handling of Capital Embedded AR Classic and PLUSCONTROL 1st Gen products. The UDP payload length specified in the IP header is not validated against actual data, allowing malformed packets to trigger information disclosure or denial-of-service conditions.

MitigationImplement proper validation of UDP length fields against IP header length and actual payload size before processing. Apply vendor-provided firmware updates when available.

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:< 2014.12
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
High
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/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 firmware version
    Locate the device or software in your environment and determine its exact model and firmware/software version. For embedded devices, check the web UI, console, or firmware metadata. For software components, check the installed version via product documentation or system inventory tools.
    Affected if The product is any of: Siemens Capital Vstar, Siemens Nucleus Net, Siemens Nucleus Readystart V3, Siemens Nucleus Source Code, Siemens Apogee Modular Building Controller Firmware, Siemens Apogee Modular Equipment Controller Firmware, Siemens Apogee Pxc Compact Firmware, or Siemens Apogee Pxc Modular
  2. Verify Nucleus Readystart V3 version if applicable
    If the deployed product is Siemens Nucleus Readystart V3, check the installed version number. Compare it against the affected range: any version prior to 2014.12 is affected.
    Affected if The product is Nucleus Readystart V3 with a version earlier than 2014.12.
  3. Confirm UDP services are enabled
    Determine whether the device has UDP services exposed or enabled. For embedded controllers, check network configuration settings, open ports, or service listings via the device console, web interface, or network scanning tools.
    Affected if UDP-based services or ports are open and reachable on the affected device.
  4. Assess network accessibility of UDP endpoints
    Evaluate whether the device with exposed UDP services can receive packets from untrusted sources. Check if the device is directly accessible from network segments where potentially malicious actors could send malformed UDP packets.
    Affected if The UDP service is accessible from network segments outside the trusted administrative zone.

You are affected if you have deployed any of the listed Siemens products with UDP services enabled and the device is reachable on the network, particularly for Nucleus Readystart V3 versions prior to 2014.12.

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 2014.12 or later
Fixed in 2014.12
Interim mitigation

Implement proper validation of UDP length fields against IP header length and actual payload size before processing. Apply vendor-provided firmware updates when available.

Fix this in Capital Vstar Scoped from the published advisory
  • Consultation8.0 h
  • Implementation16.0 h
  • Testing12.0 h
  • Review / QA8.0 h
44.0 hours of engineering $7,720
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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-2021-31345 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