The tt_cmap4_validate function in sfnt/ttcmap.c in FreeType before 2.5.4 validates a certain length field before that field's value is completely calculated, which allows remote attackers to cause a denial of service (out-of-bounds read) or possibly have unspecified other impact via a crafted cmap SFNT table.
https://security.gentoo.org/glsa/201503-05
http://www.ubuntu.com/usn/USN-2739-1
http://www.ubuntu.com/usn/USN-2510-1
http://www.securityfocus.com/bid/72986
http://www.oracle.com/technetwork/topics/security/bulletinapr2015-2511959.html
http://www.debian.org/security/2015/dsa-3188
http://rhn.redhat.com/errata/RHSA-2015-0696.html
http://lists.opensuse.org/opensuse-updates/2015-03/msg00091.html
http://lists.fedoraproject.org/pipermail/package-announce/2015-February/150162.html
http://lists.fedoraproject.org/pipermail/package-announce/2015-February/150148.html