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Simatic Wincc Runtime AdvancedApplication · Siemens

CVE-2021-27383

HIGH · 7.5 CVSS v3.1 Published 2021-05-12
Fix available
A fix is available. Upgrade to 15.1 / 16 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 SIMATIC HMI Comfort Outdoor Panels V15 7\" & 15\" (incl. SIPLUS variants) (All versions < V15.1 Update 6), SIMATIC HMI Comfort Outdoor Panels V16 7\" & 15\" (incl. SIPLUS variants) (All versions < V16 Update 4), SIMATIC HMI Comfort Panels V15 4\" - 22\" (incl. SIPLUS variants) (All versions < V15.1 Update 6), SIMATIC HMI Comfort Panels V16 4\" - 22\" (incl. SIPLUS variants) (All versions < V16 Update 4), SIMATIC HMI KTP Mobile Panels V15 KTP400F, KTP700, KTP700F, KTP900 and KTP900F (All versions < V15.1 Update 6), SIMATIC HMI KTP Mobile Panels V16 KTP400F, KTP700, KTP700F, KTP900 and KTP900F (All versions < V16 Update 4), SIMATIC WinCC Runtime Advanced V15 (All versions < V15.1 Update 6), SIMATIC WinCC Runtime Advanced V16 (All versions < V16 Update 4), SINAMICS GH150 (All versions), SINAMICS GL150 (with option X30) (All versions), SINAMICS GM150 (with option X30) (All versions), SINAMICS SH150 (All versions), SINAMICS SL150 (All versions), SINAMICS SM120 (All versions), SINAMICS SM150 (All versions), SINAMICS SM150i (All versions). SmartVNC has a heap allocation leak vulnerability in the server Tight encoder, which could result in a Denial-of-Service condition.

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

SmartVNC server contains a heap allocation memory leak in its Tight encoder component. When processing VNC remote display connections, memory allocations are made but not properly freed, causing progressive memory exhaustion that eventually leads to denial of service.

MitigationApply Siemens V15.1 Update 6 or V16 Update 4 (depending on product version) to patch the SmartVNC heap allocation leak. For SINAMICS devices without available updates, consider network segmentation to restrict VNC access.

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 Wincc Runtime AdvancedApplication
Affected:< 16= 16< 15.1= 15.1
Sinamics Sh150 FirmwareOperating system
Affected:all versions
Sinamics Sm150i FirmwareOperating system
Affected:all versions
Sinamics Gh150 FirmwareOperating system
Affected:all versions
Sinamics Gl150 FirmwareOperating system
Affected:all versions
Sinamics Gm150 FirmwareOperating system
Affected:all versions
Sinamics Sl150 FirmwareOperating system
Affected:all versions
Sinamics Sm120 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 Simatic WinCC Runtime Advanced installation
    Check the installed version of Simatic WinCC Runtime Advanced on the system. This is typically found in the product's 'About' section, installed program information, or by querying the Siemens installation database.
    Affected if The installed version is 15.1, 16, or any version lower than 15.1 or 16 (e.g., 14, 15, etc.)
  2. Identify Sinamics device firmware version
    Connect to the Sinamics drive device via its engineering interface (e.g., STARTER, Startdrive) or check the device firmware version through the device's system information or parameter display.
    Affected if The device is any Sinamics Sh150, Sm150i, Gh150, Gl150, Gm150, Sl150, or Sm120 with any firmware version installed - all versions are affected.
  3. Verify SmartVNC server presence
    Confirm that SmartVNC server component is installed or enabled as part of the Siemens software or device. This may be visible in running services, installed components, or device configuration.
    Affected if SmartVNC server is present on the system or device.
  4. Confirm Tight encoder is in use
    Check the VNC connection configuration to determine if Tight encoding is enabled or being used for remote display sessions. This setting is typically found in VNC server configuration or connection profiles.
    Affected if Tight encoding is enabled or actively used for VNC connections.

You are affected if you have Simatic WinCC Runtime Advanced versions 15.1 or 16 (or lower), or any Sinamics device (Sh150, Sm150i, Gh150, Gl150, Gm150, Sl150, Sm120) with SmartVNC running and Tight encoder active, as the memory leak will trigger during VNC sessions leading to progressive memory exhaustion.

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 15.1 / 16 or later
Fixed in 15.116
Interim mitigation

Apply Siemens V15.1 Update 6 or V16 Update 4 (depending on product version) to patch the SmartVNC heap allocation leak. For SINAMICS devices without available updates, consider network segmentation to restrict VNC access.

Fix this in Simatic Wincc Runtime Advanced Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA2.0 h
18.0 hours of engineering $3,200
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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-2021-27383 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