FTP proxy in Squid before 2.4.STABLE6 does not compare the IP addresses of control and data connections with the FTP server, which allows remote attackers to bypass firewall rules or spoof FTP server responses.
http://www.squid-cache.org/Versions/v2/2.4/bugs/
http://www.squid-cache.org/Advisories/SQUID-2002_3.txt
http://www.securityfocus.com/bid/5158
http://www.linux-mandrake.com/en/security/2002/MDKSA-2002-044.php
http://www.iss.net/security_center/static/9479.php
http://rhn.redhat.com/errata/RHSA-2002-130.html
http://rhn.redhat.com/errata/RHSA-2002-051.html
http://marc.info/?l=bugtraq&m=102674543407606&w=2
http://distro.conectiva.com.br/atualizacoes/?id=a&anuncio=000506