CVE-2020-12526

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

Description

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.

Remediation

Solution:

  • For devices running Windows but not Windows CE or TwinCAT/BSD please get a recent version of the OPC UA servers through the conventional ways and update your system. For devices running Windows CE please request a recent image via Beckhoff’s support and apply it to your device. For the product CX8091 please use firmware version "CX8091_CE600_LF_v356f_TC211R3_B2306_v2" or later. Please note that the updated OPC UA server leaves less RAM available to your application on the CX8091.

Workaround:

  • 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.

Category

5.3
CVSS
Severity: Medium
CVSS 3.1 •
CVSS 2.0 •
EPSS 0.38%
Vendor Advisory beckhoff.com
Affected: Beckhoff TwinCAT OPC UA Server
Affected: Beckhoff IPC Diagnostics UA Server
Affected: Beckhoff TF6100
Published at:
Updated at:

References

Link Tags
https://cert.vde.com/en-us/advisories/vde-2020-051 third party advisory
https://download.beckhoff.com/download/Document/product-security/Advisories/advisory-2021-001.pdf vendor advisory

Frequently Asked Questions

What is the severity of CVE-2020-12526?
CVE-2020-12526 has been scored as a medium severity vulnerability.
How to fix CVE-2020-12526?
To fix CVE-2020-12526: For devices running Windows but not Windows CE or TwinCAT/BSD please get a recent version of the OPC UA servers through the conventional ways and update your system. For devices running Windows CE please request a recent image via Beckhoff’s support and apply it to your device. For the product CX8091 please use firmware version "CX8091_CE600_LF_v356f_TC211R3_B2306_v2" or later. Please note that the updated OPC UA server leaves less RAM available to your application on the CX8091.
Is CVE-2020-12526 being actively exploited in the wild?
As for now, there are no information to confirm that CVE-2020-12526 is being actively exploited. According to its EPSS score, there is a ~0% probability that this vulnerability will be exploited by malicious actors in the next 30 days.
What software or system is affected by CVE-2020-12526?
CVE-2020-12526 affects Beckhoff TwinCAT OPC UA Server, Beckhoff IPC Diagnostics UA Server, Beckhoff TF6100.
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