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CVE Record

CVE-2020-12526: BECKHOFF: DoS-Vulnerability for TwinCAT OPC UA Server and IPC Diagnostics UA Server

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.

MediumCVSS 5.3Not KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

This vulnerability can make Beckhoff OPC UA server software stop responding to clients after repeated crafted network requests. It affects availability, not data confidentiality or integrity, and the source says IPC real-time functionality is not affected.

Executive priority

Treat as a moderate operational availability risk for industrial environments. Prioritize exposed or production-critical OPC UA servers, especially where downtime would affect monitoring, diagnostics, or operations visibility.

Technical view

CVE-2020-12526 is a CWE-20 input-validation flaw in Beckhoff TwinCAT OPC UA Server up to 2.3.0.12 and IPC Diagnostics UA Server up to 3.1.0.1. It is network-reachable, low-complexity, unauthenticated, and causes limited availability impact.

Likely exposure

Exposure is most likely where affected Beckhoff OPC UA services are reachable over plant, operations, vendor-access, or poorly segmented networks.

Exploitation context

The bundle states exploitation requires several specifically crafted requests. CISA KEV is false, and the provided sources do not show active exploitation, public exploit use, or indicators of compromise.

Researcher notes

The CVSS vector is AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L. The source bundle does not include packet details, proof-of-concept status, patch identifiers, or vendor workaround text beyond the affected product/version information.

Mitigation direction

  • Inventory Beckhoff TwinCAT OPC UA Server and IPC Diagnostics UA Server deployments.
  • Compare deployed versions against the affected version ranges in Beckhoff guidance.
  • Check Beckhoff advisory and support channels for confirmed fixed versions or workarounds.
  • Restrict OPC UA service access to trusted clients and management networks.
  • Monitor service health and alert on unexpected OPC UA unresponsiveness.

Validation and detection

  • Confirm whether TwinCAT OPC UA Server is version 2.3.0.12 or earlier.
  • Confirm whether IPC Diagnostics UA Server is version 3.1.0.1 or earlier.
  • Review firewall rules for unintended OPC UA network reachability.
  • Verify monitoring detects OPC UA service hangs or client connection failures.
  • Document compensating controls where updates are not immediately possible.
Prepared
Confidence
medium
Sources
4

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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cwe · low confidence lookup

CWE-20: Exact CWE lookup

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cve · low confidence lookup

CVE-2020-12526 mapping review

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Vulnerability profileCVE Program record
Severity
Medium
CVSS
5.3 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
0Timeline events
0ADP providers
3Source links

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
5.3CVSS 3.1MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L3.91.4Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

5.3Medium
CVSS 3.1 vector shape for CVE-2020-12526Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
BeckhoffTwinCAT OPC UA ServerunspecifiedListed
BeckhoffIPC Diagnostics UA ServerunspecifiedListed
BeckhoffTF6100unspecifiedListed
Weakness

CWE details

CWE-20

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.