The FT_Stream_EnterFrame function in base/ftstream.c in FreeType before 2.4.2 does not properly validate certain position values, which allows remote attackers to cause a denial of service (application crash) or possibly execute arbitrary code via a crafted font file.
https://bugs.launchpad.net/ubuntu/maverick/+source/freetype/+bug/617019
http://www.vupen.com/english/advisories/2010/3046
http://www.vupen.com/english/advisories/2010/3045
http://www.vupen.com/english/advisories/2010/2106
http://www.vupen.com/english/advisories/2010/2018
http://www.ubuntu.com/usn/USN-972-1
http://www.securityfocus.com/bid/42285
http://www.redhat.com/support/errata/RHSA-2010-0864.html
http://support.apple.com/kb/HT4457
http://support.apple.com/kb/HT4456
http://sourceforge.net/projects/freetype/files/freetype2/2.4.2/NEWS/view
http://secunia.com/advisories/48951
http://secunia.com/advisories/42317
http://secunia.com/advisories/42314
http://secunia.com/advisories/40982
http://secunia.com/advisories/40816
http://marc.info/?l=oss-security&m=128111955616772&w=2
http://lists.apple.com/archives/security-announce/2010//Nov/msg00003.html
http://lists.apple.com/archives/security-announce/2010//Nov/msg00000.html
http://freetype.sourceforge.net/index2.html#release-freetype-2.4.2