3proxy is a really tiny cross-platform proxy servers set, including HTTP, HTTPS, FTP, SOCKS and POP3 support.
3proxy contains a double free vulnerability in the ftpprchild() function, which frees param->hostname and calls the parsehostname() function, which in turn attempts to free param->hostname again.
A remote attacker could send a specially crafted request to the proxy, possibly resulting in a Denial of Service. Under typical configuration, the scope of this vulnerability is limited to the local network.
There is no known workaround at this time.
All 3proxy users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=net-proxy/3proxy-0.5.3j"