Buffer overflow in libpng 1.0.x before 1.0.55, 1.2.x before 1.2.45, 1.4.x before 1.4.8, and 1.5.x before 1.5.4, when used by an application that calls the png_rgb_to_gray function but not the png_set_expand function, allows remote attackers to overwrite memory with an arbitrary amount of data, and possibly have unspecified other impact, via a crafted PNG image.
The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer, leading to a buffer overflow.