This vulnerability is only present when the register_globals PHP option is set to 'on'. This has not been the default setting for PHP installs since version 4.2.0 (22-Apr-2002).
Upgrade to version 1.4.7 or higher, as it has been reported to fix this vulnerability. An upgrade is required as there are no known workarounds.
Vendor Specific News/Changelog Entry: http://www.squirrelmail.org/changelog.php ISS X-Force ID: 27632 FrSIRT Advisory: ADV-2006-2708 CVE-2006-3665 Bugtraq ID: 17005