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Capital VstarApplication · Siemens

CVE-2021-31885

HIGH · 7.5 CVSS v3.1 Published 2021-11-09
Fix available
A fix is available. Upgrade to 4.1.1 / 2017.02.4 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 APOGEE MBC (PPC) (BACnet) (All versions), APOGEE MBC (PPC) (P2 Ethernet) (All versions), APOGEE MEC (PPC) (BACnet) (All versions), APOGEE MEC (PPC) (P2 Ethernet) (All versions), APOGEE PXC Compact (BACnet) (All versions < V3.5.4), APOGEE PXC Compact (P2 Ethernet) (All versions < V2.8.19), APOGEE PXC Modular (BACnet) (All versions < V3.5.4), APOGEE PXC Modular (P2 Ethernet) (All versions < V2.8.19), Desigo PXC00-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC00-U (All versions >= V2.3 and < V6.30.016), Desigo PXC001-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC100-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC12-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC128-U (All versions >= V2.3 and < V6.30.016), Desigo PXC200-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC22-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC22.1-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC36.1-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC50-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC64-U (All versions >= V2.3 and < V6.30.016), Desigo PXM20-E (All versions >= V2.3 and < V6.30.016), Nucleus NET (All versions), Nucleus ReadyStart V3 (All versions < V2017.02.4), Nucleus ReadyStart V4 (All versions < V4.1.1), Nucleus Source Code (All versions), PLUSCONTROL 1st Gen (All versions), TALON TC Compact (BACnet) (All versions < V3.5.4), TALON TC Modular (BACnet) (All versions < V3.5.4). TFTP server application allows for reading the contents of the TFTP memory buffer via sending malformed TFTP commands. (FSMD-2021-0009)

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 vulnerability in the TFTP server component allows remote attackers to read the contents of the TFTP memory buffer by sending malformed TFTP commands, leading to information disclosure. This affects multiple Siemens building automation controllers including APOGEE MBC/MEC, PXC Compact/Modular, Desigo PXC series, and Nucleus-based products.

MitigationUpgrade affected devices to the patched version (APOGEE/TALON: V3.5.4+ for BACnet, V2.8.19+ for P2 Ethernet; Desigo: V6.30.016+). For products with no patch available, disable TFTP services or isolate devices on a restricted network segment.

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:< 2017.02.4
Nucleus Readystart V4Application
Affected:< 4.1.1
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

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
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/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. Verify TFTP server is running
    Check if the TFTP service is enabled or listening on UDP port 69. On Linux: 'netstat -uan | grep 69' or 'ss -uan | grep 69'. On embedded devices, check the service status via the admin interface or 'ps' command if SSH is available.
    Affected if TFTP server is active and exposed on the network
  2. Identify the product name
    Determine if the device is one of the affected Siemens building automation controllers: APOGEE MBC, APOGEE MEC, PXC Compact, PXC Modular, Desigo PXC series, or a Nucleus-based product. Check the device label, admin UI, or system information page.
    Affected if Device is any of the listed Siemens building automation controllers or Nucleus-based products
  3. Determine the firmware or software version
    Access the device admin interface, check system information page, or use commands like 'show version', 'ver', or read the firmware file name. For Nucleus products, check the version reported by the software or boot messages.
    Affected if Version cannot be determined or is unknown
  4. Compare against affected version ranges
    For Nucleus Readystart V3: version must be >= 2017.02.4 to be patched. For Nucleus Readystart V4: version must be >= 4.1.1 to be patched. For all other listed products (Capital Vstar, Nucleus Net, Apogee Firmware variants): ALL versions are affected since no safe version range is specified.
    Affected if Nucleus Readystart V3 < 2017.02.4, Nucleus Readystart V4 < 4.1.1, or any version of Capital Vstar, Nucleus Net, Apogee MBC/MEC Firmware, or Apogee Pxc Compact Firmware

The environment is affected if TFTP server is enabled and the device is any Siemens building automation controller or Nucleus-based product with a version that falls within or below the unpatched 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
Upgrade available Upgrade to 4.1.1 / 2017.02.4 or later
Fixed in 4.1.12017.02.4
Interim mitigation

Upgrade affected devices to the patched version (APOGEE/TALON: V3.5.4+ for BACnet, V2.8.19+ for P2 Ethernet; Desigo: V6.30.016+). For products with no patch available, disable TFTP services or isolate devices on a restricted network segment.

Recommended fix High confidence

V3.5.4 for BACnet variants; V2.8.19 for P2 Ethernet variants; V6.30.016 for Desigo PXC devices; V2017.02.4 for Nucleus ReadyStart V3; V4.1.1 for Nucleus ReadyStart V4

  1. For APOGEE PXC Compact (BACnet): Upgrade to firmware version V3.5.4 or later
  2. For APOGEE PXC Compact (P2 Ethernet): Upgrade to firmware version V2.8.19 or later
  3. For APOGEE PXC Modular (BACnet): Upgrade to firmware version V3.5.4 or later
  4. For APOGEE PXC Modular (P2 Ethernet): Upgrade to firmware version V2.8.19 or later
  5. For Desigo PXC00-E.D, PXC00-U, PXC001-E.D, PXC100-E.D, PXC12-E.D, PXC128-U, PXC200-E.D, PXC22-E.D, PXC22.1-E.D, PXC36.1-E.D, PXC50-E.D, PXC64-U, PXM20-E: Upgrade to firmware version V6.30.016 or later
  6. For Nucleus ReadyStart V3: Upgrade to version V2017.02.4 or later
  7. For Nucleus ReadyStart V4: Upgrade to version V4.1.1 or later
  8. For APOGEE MBC/MEC (all variants), Nucleus NET, Nucleus Source Code, PLUSCONTROL 1st Gen, and TALON TC Compact/Modular: Contact Siemens for patched firmware; no specific fixed version listed in available documentation
Caveat Review release notes for each product before upgrading to ensure compatibility with existing systems and configurations

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

Fix this in Capital Vstar Scoped from the published advisory
  • Consultation8.0 h
  • Implementation24.0 h
  • Testing16.0 h
  • Review / QA8.0 h
56.0 hours of engineering $9,760
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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-2021-31885 in production — separate from our analysis above.

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