When a wallet file is encrypted in bitcoin core, it uses an AES.256.CBC standard encryption.

When the password is decrypted, when the correct password is entered correctly, the password is not requested to be re-entered for the specified time or the password can be changed. AES.256.CBC is used in all of these stages.

I don't understand whether Bircoin Core interferes with the process of AES.256.CBC when encrypting or decrypting wallet.dat, when we look at the process of AES.256.CBC, without the "Initialization Vector", the process does not start and this is not a hidden information.
I could not find the initialization vector in the wallet.dat file. A separate calculation is made. When I used pywallet, it did not share me this "Initialization Vector".

Can someone who has knowledge about this issue enlighten?

Thank you.