Wrong UPX Header, Unable to Decompress with UPX

Question

I wanted to decompress a UPX file available to download from this link. http://goo.gl/Uw2a6O

However, when I decompress it using UPX command:

upx -d citadel.exe

I got this error:

upx: citadel.exe: CantUnpackException: illegal exe header

So, I edit i check its hexadecimal from this:

i.stack.imgur.com/VJ8ng.png

to this:

i.stack.imgur.com/PChDQ.png

Sorry, that I can't include more than 2 links because my reputation point in SO below 10.

Anyway, then I run this command again,

upx -d citadel.exe 

and I got the permission denied. This is the message:

upx: citade.exe: IOException: citadel.exe: Permission Denied
Upacked 1 file: 0 ok, 1 error.

The question is, how can I decompress this file using UPX tool?

Thanks

Answer 1

Finally I got it works by just restarting the command prompt and rerun upx -d citadel.exe.

thanks

Answer 2

I got a permission denied error, including running UPX in an admin cmd window. The .exe to unpack was in a different directory. Once I moved the .exe into the same directory as UPX, the permission denied error went away, even running in a non-admin cmd window.

Answer 3

I know this is not a recent post but stumbled across it and wanted to give my share.

In order for UPX to work, you need to direct your CMD prompt to the folder where upx is and the command should be the following:

upx -d [full path] 

The full path as to where you have the packed exe file.