The clientProcessRequest() function in src/client_side.c in Squid 2.6 before 2.6.STABLE12 allows remote attackers to cause a denial of service (daemon crash) via crafted TRACE requests that trigger an assertion error.
squid/src/ftp.c in Squid before 2.6.STABLE7 allows remote FTP servers to cause a denial of service (core dump) via crafted FTP directory listing responses, possibly related to the (1) ftpListingFinish and (2) ftpHtmlifyListEntry functions.
The aclMatchExternal function in Squid before 2.6.STABLE7 allows remote attackers to cause a denial of service (crash) by causing an external_acl queue overload, which triggers an infinite loop.