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CVE-2020-12526
TwinCAT 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.
This record: live connection— last retrieved: 7 November 2026 at 14:22.
Vendor
Published
13 May 2021
Last modified
17 June 2026
Taken directly from NVD, CISA or the vendor — sometimes in English, unchanged from the source.
TwinCAT 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.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Attack vector
NETWORK
Privileges required
NONE
User interaction
NONE
Confidentiality
None
Integrity
None
Availability
Limited
Probability of exploitation within 30 days
1.0%
Percentile
62e
Source: FIRST.org, updated on 6 November 2026.
Consider disabling the IPC Diagnostics Server by stopping and disabling the corresponding Windows service or service. For example this can be achieved with the following PowerShell commands: Stop-Service -Force -Name DevMgrSvr-UA Set-Service -Name DevMgrSvr-UA -StartupType Disabled Alternatively consider limiting access to the TCP port the OPC UA server is listening on. This can happen with a dedicated firewall appliance which sits in front of an affected device. Alternatively at the device the Windows firewall can be configured to limit access to the TCP port. Further guidance is provided within the "Security Guide IPC" from Beckhoff which is accessible at https://www.beckhoff.com/secguide
Our own interpretation and context for the source data above.
IACS Radar assessment
Our own interpretation and context for this vulnerability — not an official source.
IACS Radar priority score
Based on CVSS 5.3, EPSS 1.0%, industrial relevance 80/100.
Combines CVSS, EPSS, KEV status, industrial relevance and exposure relevance — a complement to, not a replacement for, the individual scores below and above.
Conditions for exploitation
Operational impact & energy relevance
Limited impact on availability; the risk lies mainly with confidentiality or integrity of process data.
Assessed as relevant to the energy sector based on: Vermeld in een officiële CISA ICS Advisory, wat directe relevantie voor industriële besturingssystemen bevestigt. Productbeschrijving komt overeen met de categorie "opc-server", een typisch OT/ICS-componenttype. Vendor "Beckhoff" is a known supplier of equipment for the energy sector. Description mentions industrial protocol: opc-ua.
Recommended defensive measures
Industrial relevance score
Automatically classified as industrially relevant based on CISA/NVD signals (see reasons).
Classified by IACS Radar-analysepijplijn (geautomatiseerd) on 7 November 2026.
IEC 62443 mapping
Automatic IACS Radar assessment based on the reported CWE weakness classification; not an official certification statement.