Overview
Siemens Totally Integrated Administrator (TIA) fails to properly set the module search path to be used by a privileged Node.js component, which can allow an unprivileged Windows user to run arbitrary code with SYSTEM privileges. The PCS neo administration console is reported to be affected as well.
Description
Siemens TIA runs a privileged Node.js component. The Node.js server fails to properly set the module search path. Because of this, Node.js will look for modules in the C:
ode_modules directory when the server is started. Because unprivileged Windows users can create subdirectories off of the system root, a user can create this directory and place a specially-crafted .js file in it to achieve arbitrary code execution with SYSTEM privileges when the server starts.
Impact
By placing a specially-crafted JS file in the C:
ode_modules directory, an unprivileged user may be able to execute arbitrary code with SYSTEM privileges on a Windows system with the vulnerable Siemens TIA or PCS neo administration console software installed.
Solution
Apply an update
This issue is addressed in TIA Administrator V1.0 SP2 Upd2. PCS neo administration console users should apply the mitigations described in Industrial Security in SIMATIC PCS neo.
For more details see Siemens Security Advisory SSA-428051.
Acknowledgements
This vulnerability was reported by Will Dormann of the CERT/CC.
This document was written by Will Dormann.
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