There is an invalid memory access in the function GfxIndexedColorSpace::mapColorToBase() located in GfxState.cc in Xpdf 4.0.0, as used in pdfalto 0.2. It can be triggered by (for example) sending a crafted pdf file to the pdftops binary. It allows an attacker to cause Denial of Service (Segmentation fault) or possibly have unspecified other impact.