dbcve.org
750 880\/040 000 FirmwareOperating system · Wago

CVE-2021-34581

HIGH · 7.5 CVSS v3.1 Published 2021-08-31
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
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
Missing Release of Resource after Effective Lifetime vulnerability in OpenSSL implementation of WAGO 750-831/xxx-xxx, 750-880/xxx-xxx, 750-881, 750-889 in versions FW4 up to FW15 allows an unauthenticated attacker to cause DoS on 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 · high confidence

A resource leak vulnerability (missing release of resource after effective lifetime) exists in the OpenSSL implementation used by WAGO 750-831, 750-880, 750-881, and 750-889 PLCs in firmware versions FW4 through FW15. An unauthenticated remote attacker can exploit this to cause denial of service by exhausting available resources.

MitigationUpdate the affected device firmware to a version beyond FW15 (e.g., FW16 or later) that contains the patched OpenSSL implementation. If firmware update is not immediately possible, network segmentation and access controls should be implemented to limit exposure.

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
750 880\/040 000 FirmwareOperating system
Affected:>= fw4, <= fw15
750 880\/025 002 FirmwareOperating system
Affected:>= fw4, <= fw15
750 880\/025 001 FirmwareOperating system
Affected:>= fw4, <= fw15
750 880\/025 000 FirmwareOperating system
Affected:>= fw4, <= fw15
750 831\/000 002 FirmwareOperating system
Affected:>= fw4, <= fw15
750 889 FirmwareOperating system
Affected:>= fw4, <= fw15
750 881 FirmwareOperating system
Affected:>= fw4, <= fw15
750 831 FirmwareOperating system
Affected:>= fw4, <= fw15

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 WAGO PLC model
    Locate the device label or check the device inventory to determine if the PLC is one of the following models: 750-831, 750-880, 750-881, or 750-889
    Affected if The model is any of 750-831, 750-880, 750-881, or 750-889
  2. Check the firmware version
    Access the PLC web interface, use WAGO e!COCKPIT software, or query the device via its management interface to retrieve the installed firmware version
    Affected if The firmware version is FW4 through FW15 inclusive (versions >= FW4 and <= FW15)
  3. Verify OpenSSL service exposure
    Check if the PLC is network-accessible and has OpenSSL-based services (typically HTTPS/web interfaces) enabled and reachable from the network
    Affected if The PLC has OpenSSL-based network services exposed and reachable from an attacker-controlled network segment
  4. Check for resource exhaustion symptoms
    Monitor the PLC for signs of resource exhaustion such as inability to establish new connections, unresponsive web interface, or service failures that coincide with high request volumes
    Affected if The device exhibits resource depletion symptoms such as connection failures or service unavailability under normal or elevated request loads

You are affected if you have a WAGO 750-831, 750-880, 750-881, or 750-889 PLC running firmware version FW4 through FW15 and the device has network-accessible OpenSSL services.

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 the affected device firmware to a version beyond FW15 (e.g., FW16 or later) that contains the patched OpenSSL implementation. If firmware update is not immediately possible, network segmentation and access controls should be implemented to limit exposure.

Recommended fix Moderate confidence

Firmware version newer than FW15 (e.g., FW16 or later)

  1. 1. Identify the specific WAGO controller model (750-831, 750-880, 750-881, or 750-889) in your environment
  2. 2. Check the current firmware version running on the affected device
  3. 3. Consult WAGO's official firmware download page or contact WAGO support to obtain a firmware version newer than FW15
  4. 4. Follow WAGO's standard firmware update procedure, which typically involves uploading the firmware file through the device's web interface or using WAGO's programming software
  5. 5. After upgrading, verify the device is operational and the OpenSSL version has been updated
Caveat Review WAGO release notes for any breaking changes between your current version and the target upgrade version

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

Fix this in 750 880\/040 000 Firmware Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing6.0 h
  • Review / QA3.0 h
15.0 hours of engineering $2,560
Get help mitigating

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,096.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2021-34581 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

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-2021-34581 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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