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750 893 FirmwareOperating system · Wago

CVE-2021-30189

CRITICAL · 9.8 CVSS v3.1 Published 2021-05-25
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
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
CODESYS V2 Web-Server before 1.1.9.20 has a Stack-based Buffer Overflow.

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

CODESYS V2 Web-Server before version 1.1.9.20 contains a stack-based buffer overflow vulnerability. This memory corruption flaw in the web server component allows remote attackers to overflow a stack-allocated buffer, potentially leading to arbitrary code execution or denial of service. The CRITICAL severity (CVSS 9.8) indicates ease of exploitation and complete impact on system confidentiality, integrity, and availability.

MitigationUpdate CODESYS V2 Web-Server to version 1.1.9.20 or later to remediate the vulnerability. If immediate patching is not feasible, restrict network access to the web server interface and implement compensating controls such as firewall rules limiting exposure to trusted networks.

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
750 893 FirmwareOperating system
Affected:< fw08
750 891 FirmwareOperating system
Affected:< fw08
750 890 FirmwareOperating system
Affected:< fw08
750 889 FirmwareOperating system
Affected:< fw15
750 885 FirmwareOperating system
Affected:< fw15
750 882 FirmwareOperating system
Affected:< fw15
750 881 FirmwareOperating system
Affected:< fw15
750 880 FirmwareOperating system
Affected:< fw16

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
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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 Wago 750 device model
    Locate the device label or use network discovery to confirm the exact model number (750-893, 891, 890, 889, 885, 882, 881, or 880)
    Affected if The device is one of these specific Wago 750 models
  2. Check the installed firmware version
    Access the device management interface or use the manufacturer's diagnostic tool to retrieve the current firmware version
    Affected if The firmware version is below fw08 (for 893/891/890), below fw15 (for 889/885/882/881), or below fw16 (for 880)
  3. Confirm the web server component is enabled
    Check the device configuration for CODESYS V2 Web-Server status or attempt to access the web interface on the standard HTTP port
    Affected if The web server is active and accessible on the network
  4. Verify network exposure of the web server
    Review firewall rules or network access controls to determine if the web server interface is reachable from untrusted networks
    Affected if The web server is exposed to remote or untrusted network segments

The environment is affected if the device is a Wago 750 series model with firmware below the specified threshold AND the CODESYS V2 Web-Server component is enabled and reachable.

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
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Update CODESYS V2 Web-Server to version 1.1.9.20 or later to remediate the vulnerability. If immediate patching is not feasible, restrict network access to the web server interface and implement compensating controls such as firewall rules limiting exposure to trusted networks.

Recommended fix High confidence

CODESYS V2 Web-Server version 1.1.9.20 or later (with corresponding device firmware: fw08/fw15/fw16 depending on model)

  1. Identify the specific 750 series device model in use (e.g., 750-893, 750-891, etc.)
  2. Locate and access the device's firmware update mechanism (typically via the device's web interface, management console, or update utility)
  3. Upgrade the device firmware to the minimum required version: fw08 for 750-893/891/890, fw15 for 750-889/885/882/881, or fw16 for 750-880
  4. After firmware update, navigate to the CODESYS V2 Web-Server component settings
  5. Upgrade the CODESYS V2 Web-Server to version 1.1.9.20 or later
  6. Verify the installation by checking the Web-Server version number
  7. Restart the Web-Server service if not automatically done by the update process
  8. Confirm the vulnerability is resolved by reviewing the updated version information
Caveat Review release notes for any breaking changes in Web-Server 1.1.9.20; test in non-production environment first as firmware updates may affect device operation

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

Fix this in 750 893 Firmware Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing4.0 h
  • Review / QA2.0 h
10.0 hours of engineering $1,720
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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-2021-30189 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