Tor is an implementation of second generation Onion Routing, a connection-oriented anonymizing communication service.
Multiple vulnerabilities have been discovered in Tor:
A remote attacker could possibly execute arbitrary code or cause a Denial of Service. Furthermore, a remote relay the user is directly connected to may be able to disclose anonymous information about that user or enumerate bridges in the user's connection.
There is no known workaround at this time.
All Tor users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=net-misc/tor-0.2.2.35"