The idna_to_ascii_4i function in lib/idna.c in libidn before 1.33 allows context-dependent attackers to cause a denial of service (out-of-bounds read and crash) via 64 bytes of input.
https://lists.gnu.org/archive/html/help-libidn/2016-07/msg00009.html
https://lists.gnu.org/archive/html/help-libidn/2015-07/msg00016.html
http://www.ubuntu.com/usn/USN-3068-1
http://www.securityfocus.com/bid/92070
http://www.openwall.com/lists/oss-security/2016/07/21/4
http://www.openwall.com/lists/oss-security/2016/07/20/6
http://www.debian.org/security/2016/dsa-3658
http://lists.opensuse.org/opensuse-updates/2016-08/msg00098.html
http://git.savannah.gnu.org/cgit/libidn.git/commit/?id=f20ce1128fb7f4d33297eee307dddaf0f92ac72d