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.

Buffer overflow in copy.c in Mutt before 1.5.23 allows remote attackers to cause a denial of service (crash) via a crafted RFC2047 header line, related to address expansion.

mutt_ssl.c in mutt 1.5.19 and 1.5.20, when OpenSSL is used, does not properly handle a '\0' character in a domain name in the subject's Common Name (CN) field of an X.509 certificate, which allows man-in-the-middle attackers to spoof arbitrary SSL servers via a crafted certificate issued by a legitimate Certification Authority, a related issue to CVE-2009-2408.