The t42_parse_encoding function in type42/t42parse.c in FreeType before 2.5.4 does not properly update the current position for immediates-only mode, which allows remote attackers to cause a denial of service (infinite loop) via a Type42 font.
https://savannah.nongnu.org/bugs/?41309
http://www.openwall.com/lists/oss-security/2015/09/25/4
http://www.openwall.com/lists/oss-security/2015/09/11/4