Mailman is a Python-based mailing list server with an extensive web interface.
Mailman contains an error in private.py which fails to properly sanitize input paths.
An attacker could exploit this flaw to obtain arbitrary files on the web server.
There is no known workaround at this time.
All Mailman users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=net-mail/mailman-2.1.5-r4"