The rfc1738_do_escape function in ftp.c for Squid 2.5 STABLE11 and earlier allows remote FTP servers to cause a denial of service (segmentation fault) via certain "odd" responses.
http://www.vupen.com/english/advisories/2005/2151
http://www.squid-cache.org/Versions/v2/2.5/bugs/#squid-2.5.STABLE11-rfc1738_do_escape
http://www.novell.com/linux/security/advisories/2005_27_sr.html
http://securitytracker.com/id?1015085
http://secunia.com/advisories/17645
http://secunia.com/advisories/17626
http://secunia.com/advisories/17513
http://secunia.com/advisories/17407
http://secunia.com/advisories/17338