CVE-2020-12526
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 · uneditedTwinCAT OPC UA Server in versions up to 2.3.0.12 and IPC Diagnostics UA Server in versions up to 3.1.0.1 from Beckhoff Automation GmbH & Co. KG are vulnerable to denial of service attacks. The attacker needs to send several specifically crafted requests to the running OPC UA server. After some of these requests the OPC UA server is no longer responsive to any client. This is without effect to the real-time functionality of IPCs.
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 confidenceTwinCAT OPC UA Server (versions up to 2.3.0.12) and IPC Diagnostics UA Server (versions up to 3.1.0.1) from Beckhoff contain a denial of service vulnerability. An unauthenticated remote attacker can send specially crafted OPC UA requests that, after multiple attempts, cause the OPC UA server to become completely unresponsive to legitimate clients. The vulnerability does not impact the real-time functionality of the IPCs themselves.
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<= 3.1.0.1<= 3.3.18<= 2.3.0.12CVSS 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
- Low
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
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 checksWork through these to decide whether this CVE applies to you.
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Identify installed TwinCAT OPC UA Server versionCheck the installed version of Beckhoff TwinCAT OPC UA Server in Windows Programs and Features, or look in the TwinCAT installation directory for version information typically found in product documentation or server configuration filesAffected if The installed version is 2.3.0.12 or lower
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Identify installed IPC Diagnostics UA Server versionCheck the installed version of Beckhoff IPC Diagnostics UA Server in Windows Programs and Features, or locate the UA server installation directory and check version information in server configuration or documentation filesAffected if The installed version is 3.1.0.1 or lower
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Identify installed TF6100 versionCheck the installed version of Beckhoff TF6100 (TwinCAT OPC UA) in Windows Programs and Features, or check the TwinCAT UI for the TF6100 component versionAffected if The installed version is 3.3.18 or lower
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Verify OPC UA server is enabled and runningCheck Windows Services for the OPC UA server service status, or verify via TwinCAT configuration that the OPC UA server feature is activated and the server is in a running stateAffected if The OPC UA server service is running and accepting connections
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Assess network exposure of OPC UA serverReview firewall rules and network configuration to determine if the OPC UA server port (default OPC UA ports 4840 or custom configured) is exposed to untrusted network segments or the internetAffected if The OPC UA server port is accessible from untrusted or external networks without proper access controls
If any affected version (TwinCAT OPC UA Server <=2.3.0.12, IPC Diagnostics UA Server <=3.1.0.1, or TF6100 <=3.3.18) is installed with the OPC UA server enabled and network-accessible, the environment is vulnerable to this denial-of-service condition.
Generated from the published advisory. Verify against your own configuration.
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 dataApply vendor-provided patches or upgrade to versions beyond 2.3.0.12 for TwinCAT OPC UA Server and beyond 3.1.0.1 for IPC Diagnostics UA Server. Additionally, restrict network access to OPC UA servers using firewalls or network segmentation to limit exposure to untrusted attackers.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA2.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2020-12526 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2020-12526 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- 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
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