The opj_pi_update_decode_poc function in pi.c in OpenJPEG, as used in PDFium in Google Chrome before 48.0.2564.109, miscalculates a certain layer index value, which allows remote attackers to cause a denial of service (out-of-bounds read) via a crafted PDF document.
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.