Description

The default installation path of the TwinCAT XAR 3.1 software in all versions is underneath C:\TwinCAT. If the directory does not exist it and further subdirectories are created with permissions which allow every local user to modify the content. The default installation registers TcSysUI.exe for automatic execution upon log in of a user. If a less privileged user has a local account he or she can replace TcSysUI.exe. It will be executed automatically by another user during login. This is also true for users with administrative access. Consequently, a less privileged user can trick a higher privileged user into executing code he or she modified this way. By default Beckhoff’s IPCs are shipped with TwinCAT software installed this way and with just a single local user configured. Thus the vulnerability exists if further less privileged users have been added.

Severity

 

CVSS Version 3.x CVSS Version 2.0

CVSS 3.x Severity and Metrics:

CNA:  CERT VDE

Base Score:  7.3 HIGH

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

NVD Analysts use publicly available information to associate vector strings and CVSS scores. We also display any CVSS information provided within the CVE List from the CNA.

Note: The NVD and the CNA have provided the same score. When this occurs only the CNA information is displayed, but the Acceptance Level icon for the CNA is given a checkmark to signify NVD concurrence.

CVSS 2.0 Severity and Metrics:

NIST: NVD

Base Score:  6.0 MEDIUM

Vector:  (AV:N/AC:M/Au:S/C:P/I:P/A:P)

NVD Analysts use publicly available information to associate vector strings and CVSS scores. We also display any CVSS information provided within the CVE List from the CNA.

Note: NVD Analysts have published a CVSS score for this CVE based on publicly available information at the time of analysis. The CNA has not provided a score within the CVE List.

References to Advisories, Solutions, and Tools

By selecting these links, you will be leaving NIST webspace. We have provided these links to other web sites because they may have information that would be of interest to you. No inferences should be drawn on account of other sites being referenced, or not, from this page. There may be other web sites that are more appropriate for your purpose. NIST does not necessarily endorse the views expressed, or concur with the facts presented on these sites. Further, NIST does not endorse any commercial products that may be mentioned on these sites. Please address comments about this page to nvd@nist.gov.

Hyperlink	Resource
https://cert.vde.com/en-us/advisories/vde-2020-037	Third Party Advisory

Weakness Enumeration

CWE-ID	CWE Name	Source
CWE-276	Incorrect Default Permissions	NIST   CERT VDE

Known Affected Software Configurations Switch to CPE 2.2

CPEs loading, please wait.

Denotes Vulnerable Software
Are we missing a CPE here? Please let us know.

Change History

1 change records found show changes

Initial Analysis by NIST 12/03/2020 11:47:53 AM

Action	Type	Old Value	New Value
Added	CPE Configuration		OR *cpe:2.3:a:beckhoff:twincat_extended_automation_runtime:3.1:*:*:*:*:*:*:*
Added	CVSS V2		NIST (AV:N/AC:M/Au:S/C:P/I:P/A:P)
Added	CVSS V2 Metadata		Victim must voluntarily interact with attack mechanism
Added	CVSS V3.1		NIST AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H
Added	CWE		NIST CWE-276
Changed	Reference Type	https://cert.vde.com/en-us/advisories/vde-2020-037 No Types Assigned	https://cert.vde.com/en-us/advisories/vde-2020-037 Third Party Advisory