CVE-2019-17263

In libyal libfwsi before 20191006, libfwsi_extension_block_copy_from_byte_stream in libfwsi_extension_block.c has a heap-based buffer over-read because rejection of an unsupported size only considers values less than 6, even though values of 6 and 7 are also unsupported. NOTE: the vendor has disputed this as described in the GitHub issue