ImageMagick is free and open-source software used for editing and manipulating digital images. Prior to versions 7.1.2-16 and 6.9.13-41, a 32-bit unsigned integer overflow in the XWD (X Windows) encoder can cause an undersized heap buffer allocation. When writing a extremely large image an out of bounds heap write can occur. This vulnerability is fixed in 7.1.2-16 and 6.9.13-41.