If you are rooted, you could extract the /system/lib/libstagefright* files from the very latest compatible TW firmware providing it itself has had the patch coded in.
As far as I know the only patched firmware for GT-i9505 at the moment is I9505VJUHOG1, and this still has 1 vulnerability (CVE-2015-3864) but the other 6 have been addressed.