CVE-2020-12526Network attack vector

Unauthenticated service stoppage via OPC UA stack overflow

Published May 13, 2021 · Updated Sep 16, 2024

Denial of service in Beckhoff OPC UA servers allows remote attackers to stop affected servers by sending crafted packets over TCP. The servers improperly validate a repeated series of OPC UA packets, provoking a stack overflow that halts the service until an administrator restarts it. No local account or OPC UA authentication is required when the listening port is reachable, and the IPC's real-time runtime remains operational.

CVSS severity5.3
Medium
EPSS probability0.95%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Denial of service in Beckhoff OPC UA servers allows remote attackers to stop affected servers by sending crafted packets over TCP. The servers improperly validate a repeated series of OPC UA packets, provoking a stack overflow that halts the service until an administrator restarts it. No local account or OPC UA authentication is required when the listening port is reachable, and the IPC's real-time runtime remains operational.

The record

CVE
CVE-2020-12526
Published
May 13, 2021
Updated
Sep 16, 2024
Vendor
Beckhoff Automation GmbH & Co. KG
Product
IPC Diagnostics UA Server
Classifications
CWE-20, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 13, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <=3.1.0.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Beckhoff Automation GmbH & Co. KG · IPC Diagnostics UA Serverversion=unspecified <=3.1.0.1
Beckhoff Automation GmbH & Co. KG · TF6100 TwinCAT 3 OPC UAversion=unspecified <=3.3.18
Beckhoff Automation GmbH & Co. KG · TwinCAT OPC UA Serverversion=unspecified <=2.3.0.12

Published CVSS scores

5.3CERT@VDECVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
5.0NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
5.3NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-20Improper Input Validation
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo