Mailman is a python-based mailing list server with an extensive web interface.
Mailman contains an unspecified vulnerability in the handling of request emails.
By sending a carefully crafted email request to the mailman server an attacker could obtain member passwords.
There is no known workaround at this time.
All users of Mailman should upgrade to the latest stable version:
# emerge sync
# emerge -pv ">=net-mail/mailman-2.1.5"
# emerge ">=net-mail/mailman-2.1.5"