Buffer overflow in the FileReadGIF function in tkImgGIF.c for Tk Toolkit 8.4.12 and earlier, and 8.3.5 and earlier, allows user-assisted attackers to cause a denial of service (segmentation fault) via an animated GIF in which the first subimage is smaller than a subsequent subimage, which triggers the overflow in the ReadImage function, a different vulnerability than CVE-2007-5137.
The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.