In Carbon 4.4.x code I could see that, 'sh' command is used to determine whether the operating system is Windows or not. So based on the code you have pointed,it has changed to 'bash' and now the new 'bash' option is not working on some of the Windows systems. I could confirm that old carbon 4.4.x related 'sh' command still works without any issue and I haven't noticed anyone faced a similar issue(in Dev list or StackOverflow) with any of the official WSO2 products up to now.
So I personally believe that, the code you have pointed it is not working as expected(on the expected use cases) and need to be fixed it properly.
I was able to reproduce your issue. This issue is caused due to an uncompleted bash installation in Windows 10.
With windows 10 (10th year anniversary edition) users were given the option to install bash within windows. So once you have installed Windows sub system for Linux(beta) feature it actually doesn't completely install all of its features. This creates a 'bash.exe' in system32 folder and it will be installed when the "bash" command runs.
In carbon-kernel  we try to write a PPID using a bash command. In windows environment we expect an exception when trying to execute this step since bash is not available in windows. But in this case bash is available in the windows environment and an exception is not generated. So the process continues and it try to read a line in  but it hangs there because once we execute the "bash" command it tries to install bash in windows(user input is required to install it)
So, to resolve this issue we can install bash completely by running "bash" command in command prompt or remove the Windows sub system for Linux(beta) feature.
I hope this is the same reason for your issue as well. (you can check whether you have partially installed bash by typing "bash" in command prompt. This will ask you to install it properly.)
Let us know if this helped you to resolve the issue.
PS: Complete tutorial on installing bash in windows 10 is available in .