Multiple stack-based buffer overflows in pdf_shade4.c in MuPDF before commit 20091125231942, as used in SumatraPDF before 1.0.1, allow remote attackers to cause a denial of service and possibly execute arbitrary code via a /Decode array for certain types of shading that are not properly handled by the (1) pdf_loadtype4shade, (2) pdf_loadtype5shade, (3) pdf_loadtype6shade, and (4) pdf_loadtype7shade functions.  NOTE: some of these details are obtained from third party information.