Bug#960062: libemail-mime-perl: DoS on excessive or deeply nested parts

[Perl Email user]

Package: libemail-mime-perl
Version: 1.946-1
Severity: important
Tags: upstream

Messages with too many tiny MIME parts can OOM on split().

Messages with many nested MIME parts can also fail on deep
recursion (Email::MIME->new calls ->subparts, ->subparts calls
->new, ad infinitum).

Smallish messages can generate these, since the a boundary
only needs to be 4 bytes "--a\n" and the header+body of
each part can just be 4 bytes "x:y\n\n", too.

Perl takes 42 bytes to represent a 4 byte string on 64-bit:

	use Devel::Size; say Devel::Size::total_size("--\n\n")

This affects many other MIME parsers, too.