SquirrelMail is a webmail package written in PHP. It supports IMAP and SMTP and can optionally be installed with SQL support.
SquirrelMail fails to properly sanitize certain strings when decoding specially-crafted strings, which can lead to PHP file inclusion and XSS.
By sending a specially-crafted URL, an attacker can execute arbitrary code from the local system with the permissions of the web server. Furthermore by enticing a user to load a specially-crafted URL, it is possible to display arbitrary remote web pages in Squirrelmail's frameset and execute arbitrary scripts running in the context of the victim's browser. This could lead to a compromise of the user's webmail account, cookie theft, etc.
The arbitrary code execution is only possible with "register_globals" set to "On". Gentoo ships PHP with "register_globals" set to "Off" by default. There are no known workarounds for the other issues at this time.
All SquirrelMail users should upgrade to the latest version:
# emerge --sync # emerge --ask --oneshot --verbose ">=mail-client/squirrelmail-1.4.4"
Note: Users with the vhosts USE flag set should manually use webapp-config to finalize the update.