The (1) cf2_initLocalRegionBuffer and (2) cf2_initGlobalRegionBuffer functions in cff/cf2ft.c in FreeType before 2.5.3 do not properly check if a subroutine exists, which allows remote attackers to cause a denial of service (assertion failure), as demonstrated by a crafted ttf file.
http://www.ubuntu.com/usn/USN-2148-1
http://www.openwall.com/lists/oss-security/2014/03/12/4