MIME-tools is a Perl module containing functions to handle MIME attachments.
MIME-tools doesn't correctly parse attachment boundaries with an empty name (boundary="").
An attacker could send a carefully crafted email and evade detection on some email virus-scanning programs using MIME-tools for attachment decoding.
There is no known workaround at this time.
All MIME-tools users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=dev-perl/MIME-tools-5.415"