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Sinumerik 808d FirmwareOperating system · Siemens

CVE-2021-37199

HIGH · 7.5 CVSS v3.1 Published 2021-10-12
Fix available
A fix is available. Upgrade to 4.95 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 SINUMERIK 808D (All versions), SINUMERIK 828D (All versions < V4.95). Affected devices don't process correctly certain special crafted packets sent to port 102/tcp, which could allow an attacker to cause a denial-of-service in the device.

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 denial-of-service vulnerability exists in Siemens SINUMERIK 808D and 828D CNC controllers where specially crafted packets sent to port 102/tcp (the Siemens S7/OPC communication port) are not properly processed, causing the device to become unresponsive or fail.

MitigationFor SINUMERIK 828D, upgrade to firmware V4.95 or later. For SINUMERIK 808D (all versions, no patch available), implement compensating controls such as network segmentation, firewalls, or blocking unauthorized access to port 102/tcp.

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
Sinumerik 808d FirmwareOperating system
Affected:all versions
Sinumerik 828d FirmwareOperating system
Affected:< 4.95

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 SINUMERIK model
    Check the device label, HMI interface, or system documentation to confirm whether the CNC controller is a Sinumerik 808D or 828D model.
    Affected if Device is a Sinumerik 808D (all versions affected) or Sinumerik 828D with firmware below V4.95
  2. Determine the firmware version on Sinumerik 828D
    On the 828D HMI, navigate to System > System Info > Version, or access the bootloader screen during startup to view the firmware version. Compare against V4.95.
    Affected if Firmware version is below V4.95 (if the model is 828D)
  3. Verify port 102/tcp is accessible
    From an external host, run 'nc -zv <device_ip> 102' or 'nmap -p 102 <device_ip>' to test TCP connectivity to port 102.
    Affected if Port 102/tcp responds or accepts connections from any network segment accessible to untrusted users
  4. Review network exposure of the CNC controller
    Examine network diagrams, firewall rules, or VLAN configurations to determine if the device with port 102/tcp is reachable from production networks, the internet, or untrusted segments.
    Affected if The controller is on a network where unauthorized or untrusted parties can reach port 102/tcp

If the device is a Sinumerik 808D or a Sinumerik 828D with firmware below V4.95, and port 102/tcp is accessible from untrusted networks, the environment is vulnerable.

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 4.95 or later
Fixed in 4.95
Interim mitigation

For SINUMERIK 828D, upgrade to firmware V4.95 or later. For SINUMERIK 808D (all versions, no patch available), implement compensating controls such as network segmentation, firewalls, or blocking unauthorized access to port 102/tcp.

Recommended fix Moderate confidence

Sinumerik 828D: Upgrade to firmware V4.95 or later

  1. Identify the current firmware version of the Sinumerik 828D device by accessing the system information or using SINUMERIK operate interface
  2. Obtain the firmware upgrade package for Sinumerik 828D version 4.95 or later from Siemens (via cert-portal.siemens.com or official Siemens support channels)
  3. Follow Siemens standard firmware update procedure for Sinumerik 828D - typically involves transferring the firmware via USB or network to the NC/PLC, then performing a firmware reload
  4. After upgrade, verify the new firmware version is V4.95 or higher
  5. For Sinumerik 808D: Contact Siemens directly for remediation options as no fixed version is specified in the advisory
  6. Consider network segmentation and firewall rules to restrict access to port 102/tcp to trusted hosts only as an additional mitigation
Caveat Review Siemens upgrade documentation for any operational considerations during firmware update; ensure proper backup of CNC programs and parameters before upgrading

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

Fix this in Sinumerik 808d Firmware Scoped from the published advisory
  • Consultation6.0 h
  • Implementation8.0 h
  • Testing8.0 h
  • Review / QA4.0 h
26.0 hours of engineering $4,560
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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-2021-37199 in production — separate from our analysis above.

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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