The Instance::HandleInputEvent function in pdf/instance.cc in the PDFium component in Google Chrome before 38.0.2125.101 interprets a certain -1 value as an index instead of a no-visible-page error code, which allows remote attackers to cause a denial of service (out-of-bounds read) via unspecified vectors.
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.