An integer overflow issue was discovered in ImageMagick's ExportIndexQuantum() function in MagickCore/quantum-export.c. Function calls to GetPixelIndex() could result in values outside the range of representable for the 'unsigned char'. When ImageMagick processes a crafted pdf file, this could lead to an undefined behaviour or a crash.
https://lists.debian.org/debian-lts-announce/2023/03/msg00008.html
https://github.com/ImageMagick/ImageMagick6/commit/553054c1cb1e4e05ec86237afef76a32cd7c464d
https://github.com/ImageMagick/ImageMagick/pull/3083
https://github.com/ImageMagick/ImageMagick/commit/5af1dffa4b6ab984b5f13d1e91c95760d75f12a6