The SillMap::readFace function in FeatureMap.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, mishandles a return value, which allows remote attackers to cause a denial of service (missing initialization, NULL pointer dereference, and application crash) via a crafted Graphite smart font.