Need to match http://hostname//etc/passwd

Hi, I have a security issue in my software that makes the entire filesystem accessible to public like this: http://hostname//etc/passwd

I have already fixed but while i upgrade i need nginx to block this kind of requests (i'm using it as a reverse proxy). I've tried using:

location ~ ^//
location ~* //
location ~* ^//.*
and so on... none of them worked for me

Anyone knows how to do this? Thanks so much...