Problem with upload of attachment confirmed.  Though I have FTP-access to the server I am not permitted to CHMOD this folder and its content!
You will have to wait for Ritesh to show up in the morning.  Fixing this issue takes ROOT-acces to the RedHat OS from a remote SHH-shell, I believe!  It is crazy.  We had some similar issues with the attachments folder of the FAQ-system.  An LAMP config issue with the Red Hat systems.  I stick to SuSE myself! 
Could you explain the buffer-overrun issue in VERBOSE mode?  😉
How to reproduce?
It has not been reported before,  I myself haven't either had this.
Did you install 'over' existing version or in a new folder?