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750 823 FirmwareOperating system · Wago

CVE-2021-34595

HIGH · 8.1 CVSS v3.1 Published 2021-10-26
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
87/100
Remediation priority · High
Remotely reachable 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 crafted request with invalid offsets may cause an out-of-bounds read or write access in CODESYS V2 Runtime Toolkit 32 Bit full and PLCWinNT prior to versions V2.4.7.56, resulting in a denial-of-service condition or local memory overwrite.

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 memory corruption vulnerability in CODESYS V2 Runtime Toolkit 32 Bit and PLCWinNT allows attackers to send crafted requests with invalid offsets, causing out-of-bounds read/write access. This can result in denial-of-service or local memory overwrite.

MitigationUpgrade CODESYS V2 Runtime Toolkit and PLCWinNT to version V2.4.7.56 or later to remediate the vulnerability.

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
750 823 FirmwareOperating system
Affected:< fw10
750 829 FirmwareOperating system
Affected:< fw17
750 831 FirmwareOperating system
Affected:< fw17
750 832 FirmwareOperating system
Affected:< fw10
750 852 FirmwareOperating system
Affected:< fw17
750 862 FirmwareOperating system
Affected:< fw10
750 880 FirmwareOperating system
Affected:< fw17
750 881 FirmwareOperating system
Affected:< fw17

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
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/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 Wago device model
    Locate the device label or check system documentation to confirm the specific 750 series model (823, 829, 831, 832, 852, 862, 880, or 881)
    Affected if The device is one of the listed models and the firmware version is below the threshold
  2. Check firmware version
    Access the device management interface or use the vendor-provided firmware version check utility to retrieve the current firmware version
    Affected if The installed firmware version is below fw10 for models 750-823, 750-832, or 750-862; or below fw17 for models 750-829, 750-831, 750-852, 750-880, or 750-881
  3. Confirm CODESYS V2 Runtime Toolkit is in use
    Check the runtime software installed on the device or PLC project configuration to verify CODESYS V2 Runtime Toolkit 32 Bit or PLCWinNT is deployed
    Affected if The CODESYS V2 Runtime Toolkit 32 Bit or PLCWinNT is running and the firmware version is below the affected thresholds

The environment is affected if it contains a Wago 750 series PLC (823, 829, 831, 832, 852, 862, 880, or 881) with firmware below the specified version thresholds and uses the CODESYS V2 Runtime Toolkit.

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

Upgrade CODESYS V2 Runtime Toolkit and PLCWinNT to version V2.4.7.56 or later to remediate the vulnerability.

Recommended fix High confidence

CODESYS V2 Runtime Toolkit V2.4.7.56 (and corresponding firmware updates for 750 series controllers: fw10, fw17, or fw17 depending on model)

  1. Identify the specific 750 series controller model from the affected list (750 823, 750 829, 750 831, 750 832, 750 852, 750 862, 750 880, or 750 881)
  2. Check the current firmware version installed on the controller
  3. Contact the controller manufacturer or CODESYS support to obtain the firmware update that addresses CVE-2021-34595
  4. Apply the firmware upgrade to bring the controller to the minimum fixed firmware version (fw10 or fw17 depending on model)
  5. Alternatively, if using CODESYS V2 Runtime Toolkit directly, upgrade to version V2.4.7.56 or later
  6. After upgrade, verify the firmware/runtime version matches the fixed release
  7. Test the system to ensure normal operation
Caveat Verify compatibility with existing project configurations and any third-party libraries before upgrading

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

Fix this in 750 823 Firmware Scoped from the published advisory
  • Consultation4.0 h
  • Implementation4.0 h
  • Testing8.0 h
  • Review / QA4.0 h
20.0 hours of engineering $3,440
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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-2021-34595 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