Multiple buffer overflows in libtiff before 4.0.3 allow remote attackers to cause a denial of service (out-of-bounds write) via a crafted (1) extension block in a GIF image or (2) GIF raster image to tools/gif2tiff.c or (3) a long filename for a TIFF image to tools/rgb2ycbcr.c.  NOTE: vectors 1 and 3 are disputed by Red Hat, which states that the input cannot exceed the allocated buffer size.