The write_one_header function in mutt 1.5.23 does not properly handle newline characters at the beginning of a header, which allows remote attackers to cause a denial of service (crash) via a header with an empty body, which triggers a heap-based buffer overflow in the mutt_substrdup function.
https://security.gentoo.org/glsa/201701-04
http://www.securitytracker.com/id/1031266
http://www.securityfocus.com/bid/71334
http://www.openwall.com/lists/oss-security/2014/11/27/9
http://www.debian.org/security/2014/dsa-3083
http://lists.opensuse.org/opensuse-security-announce/2015-01/msg00002.html