The TtfUtil:LocaLookup function in TtfUtil.cpp in Libgraphite in Graphite 2 1.2.4, as used in Mozilla Firefox before 43.0 and Firefox ESR 38.x before 38.6.1, incorrectly validates a size value, which allows remote attackers to obtain sensitive information or cause a denial of service (out-of-bounds read and application crash) via a crafted Graphite smart font.
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.