Null source pointer passed as an argument to memcpy() function within TIFFReadDirectory() in tif_dirread.c in libtiff versions from 4.0 to 4.3.0 could lead to Denial of Service via crafted TIFF file. For users that compile libtiff from sources, a fix is available with commit 561599c.
LibTIFF 4.3.0 has an out-of-bounds read in _TIFFmemcpy in tif_unix.c in certain situations involving a custom tag and 0x0200 as the second word of the DE field.