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.
The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.