The CJBig2_SymbolDict class in fxcodec/jbig2/JBig2_SymbolDict.cpp in PDFium, as used in Google Chrome before 47.0.2526.73, allows remote attackers to cause a denial of service (out-of-bounds memory access) or possibly have unspecified other impact via a PDF document containing crafted data with JBIG2 compression.
The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.