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…

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.