Multiple Heap-based Buffer Overflow in the do_msg() function

[jbrandwood]

aka https://nvd.nist.gov/vuln/detail/CVE-2019-14274
aka https://sourceforge.net/p/mcpp/bugs/13/

This has been fixed in Debian as a patch 05-gniibe-fix-13.patch, and (slightly differently) here ...

jbrandwood/mcpp@70a33a4