Beckhoff's TwinCAT 3 Engineering software is intented to craft automation projects consisting of a set of files which are stored locally as files underneath an individual folder or in a packed file. The TwinCAT 3 Engineering stores user settings and preferences among the non packed local files which are relevant to continue former work on the project conventienly. TwinCAT 3 Engineering stores such settings in files which are called "Solution User Options (.suo) File". When such settings are manipulated or crafted by an adversary in a specific way then TwinCAT 3 Engineering executes arbitrary commands as determined by these settings when the user uses TwinCAT 3 Engineering to open the project. These arbitrary commands are executed in the user context.

Please note that solution user option files should not be checked in to source code control. This is also a best practice when working with source code projects and solutions. For example, see https://learn.microsoft.com/en-us/visualstudio/extensibility/internals/solution-user-options-dot-suo-file and https://infosys.beckhoff.com/content/1033/tc3_sourcecontrol/14604066827.html.

The vulnerability is similar to older vulnerabilities that were addressed in the CODESYS Development System V3 product from CODESYS GmbH with CVE-2021-21864, CVE-2021-21865, CVE-2021-21866, CVE-2021-21867, CVE-2021-21868, CVE-2021-21869, and the associated Advisory 2021-13 from CODESYS GmbH.

An unauthenticated attacker can trick a local user into executing arbitrary commands by opening a deliberately manipulated project file with an affected engineering tool. These arbitrary commands are executed in the user context.