How to avoid load system DLL while creating application using WPF

Question

How to avoid load system DLL while creating application using WPF

Prashant Sharma 0

I have application in WPF C#, When I run process mon I can see list of System DLL

cryptsp.dll
CRYPTBASE.dll
bcrypt.dll
MSVCP140_CLR0400.dll
profapi.dll
USP10.dll
msls31.dll
NTASN1.dll By placing a malicious DLL with the same name in the application directory, arbitrary code execution was achieved. How to avoid such case.

Viorel 127K Reputation points

2025-10-23T10:53:07.52+00:00

I think that the malicious programs, that are able to put malicious DLLs, do not really need to put malicious DLLs in order to perform malicious activities.

2 answers

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Viorel 127K Reputation points

2025-10-23T10:53:07.52+00:00

I think that the malicious programs, that are able to put malicious DLLs, do not really need to put malicious DLLs in order to perform malicious activities.

Answer 1

Susmitha T (INFOSYS LIMITED) 2,695 Microsoft External Staff

Thanks for reaching out!

To prevent, you can restrict your WPF application from loading malicious system DLLs by calling
SetDefaultDllDirectories(LOAD_LIBRARY_SEARCH_SYSTEM32) early in the app startup (e.g., in App.xaml.cs). This ensures only the trustable system locations like System32 are used for DLL loading.

Additionally, install the app in protected folders (e.g., program files), avoid loading DLLs by name without full paths, and sign your binaries for integrity.

Let me know if you need any further help with this. We'll be happy to assist.

If you find this helpful, Kindly mark the provided solution as "Accept Answer", so that others in the community facing similar issues can easily find the solution. Your contribution is highly appreciated.

Susmitha T (INFOSYS LIMITED) 2,695 Reputation points Microsoft External Staff

2025-10-31T05:47:24.03+00:00

"Hope you're doing well. We're following up on the thread. Please let us know whether the issue persists or has been resolved. If the issue has been resolved, kindly mark the response as "answered". We'll close this thread by 5th November, so we are hoping for your reply before that".
Susmitha T (INFOSYS LIMITED) 2,695 Reputation points Microsoft External Staff

2025-11-03T06:05:53.26+00:00

"Hope you're doing well. We're following up on the thread. Please let us know whether the issue persists or has been resolved. If the issue has been resolved, kindly mark the response as "answered". We'll close this thread by 5th November, so we are hoping for your reply before that".
Susmitha T (INFOSYS LIMITED) 2,695 Reputation points Microsoft External Staff

2025-11-05T06:09:57.92+00:00

Since the thread has been open for a considerable time, we will be proceeding to close the thread. If the issue persists or reoccurs, please feel free to raise a new thread. We’ll be happy to assist you further.

Answer 2

Bruce (SqlWork.com) 84,086

You get around this by only using signed dlls. Most system dlls are signed. If you are creating your own, then you must sign them:

https://learn.microsoft.com/en-us/dotnet/standard/assembly/sign-strong-name

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How to avoid load system DLL while creating application using WPF

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