functions/imap_general.php in SquirrelMail before 1.4.21 does not properly handle 8-bit characters in passwords, which allows remote attackers to cause a denial of service (disk consumption) by making many IMAP login attempts with different usernames, leading to the creation of many preferences files.

Multiple cross-site request forgery (CSRF) vulnerabilities in SquirrelMail 1.4.19 and earlier, and NaSMail before 1.7, allow remote attackers to hijack the authentication of unspecified victims via features such as send message and change preferences, related to (1) functions/mailbox_display.php, (2) src/addrbook_search_html.php, (3) src/addressbook.php, (4) src/compose.php, (5) src/folders.php, (6) src/folders_create.php, (7) src/folders_delete.php, (8) src/folders_rename_do.php, (9) src/folders_rename_getname.php, (10) src/folders_subscribe.php, (11) src/move_messages.php, (12) src/options.php, (13) src/options_highlight.php, (14) src/options_identities.php, (15) src/options_order.php, (16) src/search.php, and (17) src/vcard.php.

functions/mime.php in SquirrelMail before 1.4.18 does not protect the application's content from Cascading Style Sheets (CSS) positioning in HTML e-mail messages, which allows remote attackers to spoof the user interface, and conduct cross-site scripting (XSS) and phishing attacks, via a crafted message.

The map_yp_alias function in functions/imap_general.php in SquirrelMail before 1.4.18 and NaSMail before 1.7 allows remote attackers to execute arbitrary commands via shell metacharacters in a username string that is used by the ypmatch program.

Multiple cross-site scripting (XSS) vulnerabilities in SquirrelMail before 1.4.18 and NaSMail before 1.7 allow remote attackers to inject arbitrary web script or HTML via vectors involving (1) certain encrypted strings in e-mail headers, related to contrib/decrypt_headers.php; (2) PHP_SELF; and (3) the query string (aka QUERY_STRING).

Multiple cross-site scripting (XSS) vulnerabilities in SquirrelMail 1.4.0 through 1.4.9 allow remote attackers to inject arbitrary web script or HTML via the (1) mailto parameter in (a) webmail.php, the (2) session and (3) delete_draft parameters in (b) compose.php, and (4) unspecified vectors involving "a shortcoming in the magicHTML filter."

Dynamic variable evaluation vulnerability in compose.php in SquirrelMail 1.4.0 to 1.4.7 allows remote attackers to overwrite arbitrary program variables and read or write the attachments and preferences of other users.

PHP remote file inclusion vulnerability in functions/plugin.php in SquirrelMail 1.4.6 and earlier, if register_globals is enabled and magic_quotes_gpc is disabled, allows remote attackers to execute arbitrary PHP code via a URL in the plugins array parameter. NOTE: this issue has been disputed by third parties, who state that Squirrelmail provides prominent warnings to the administrator when register_globals is enabled. Since the varieties of administrator negligence are uncountable, perhaps this type of issue should not be included in CVE. However, the original developer has posted a security advisory, so there might be relevant real-world environments under which this vulnerability is applicable

CRLF injection vulnerability in SquirrelMail 1.4.0 to 1.4.5 allows remote attackers to inject arbitrary IMAP commands via newline characters in the mailbox parameter of the sqimap_mailbox_select command, aka "IMAP injection."

webmail.php in SquirrelMail 1.4.0 to 1.4.5 allows remote attackers to inject arbitrary web pages into the right frame via a URL in the right_frame parameter. NOTE: this has been called a cross-site scripting (XSS) issue, but it is different than what is normally identified as XSS.