Windows builtin utility for extracting cab or msu files is expand
Usage is simple if you want to extract all files. Parameter -F defines the files to extract, the second parameter is the msu file and the third the directory to extract the files to. The directory must exist.
mkdir windows10.0-kb4056892-x64 D:\temp> expand -F:* windows10.0-kb4056892-x64_.msu windows10.0-kb4056892-x64 windows10.0-kb4056892-x64\WSUSSCAN.cab.... windows10.0-kb4056892-x64\Windows10.0-K.... windows10.0-kb4056892-x64\Windows10.0-K.... windows10.0-kb4056892-x64\Windows10.0-K.....
The msu files contains usually 4 files: WSUSSCAN.cab, the cab files with update files and a txt and xml files which describes the update.
To extract all files run expand against the cab file. Same procudure as above. First create a folder and extract files to it
D:\temp> cd windows10.0-kb4056892-x64 D:\temp\windows10.0-kb4056892-x64> mkdir cabextracted D:\temp\windows10.0-kb4056892-x64> expand -F:* Windows10.0-KB4056892-x64.cab cabextracted ...