tiff: Null source pointer passed as an argument to memcpy in TIFFFetchNormalTag() in tif_dirread.c

A flaw was found in LibTIFF where a NULL source pointer passed as an argument to the memcpy function within the TIFFFetchNormalTag in tifdirread.c. This flaw allows an attacker with a crafted TIFF file to cause a crash that leads to a denial of service...