dng_validate sRGB overexposed

Hi everyone, 

I use dng_validate.exe to post-process DNG files, but I have a problem. When I save the output in sRBG colorspace (or any other colorspace) the images are over-exposed. When I post-process the DNG files using Rawtherapee or Fast CinemaDNG and save the output in sRGB space I don't have this over-exposure problem. What might be the reason, and how can I solve it? 

Thank you in advance.