Cross-site scripting (XSS) vulnerability in the private message box implementation (privmsg.php) in phpBB 2.0.x allows remote authenticated users to inject arbitrary web script or HTML via the "Message body" field in a message to a non-existent user.

PHP remote file inclusion vulnerability in /includes/kb_constants.php in Knowledge Base Mod for PHPbb 2.0.2 and earlier allows remote attackers to execute arbitrary PHP code via a URL in the module_root_path parameter.

The gen_rand_string function in phpBB 2.0.19 uses insufficiently random data (small value space) to create the activation key ("validation ID") that is sent by e-mail when establishing a password, which makes it easier for remote attackers to obtain the key and modify passwords for existing accounts or create new accounts.

Cross-site request forgery (CSRF) vulnerability in phpBB 2.0.19, when Link to off-site Avatar or bbcode (IMG) are enabled, allows remote attackers to perform unauthorized actions as a logged in user via a link or IMG tag in a user profile, as demonstrated using links to (1) admin/admin_users.php and (2) modcp.php.

phpBB 2.0.19 and earlier allows remote attackers to cause a denial of service (application crash) by (1) registering many users through profile.php or (2) using search.php to search in a certain way that confuses the database.

SQL injection vulnerability in phpBB 2 before 2.0.18 allows remote attackers to execute arbitrary SQL commands via the topic type.

A "missing request validation" error in phpBB 2 before 2.0.18 allows remote attackers to edit private messages of other users, probably by modifying certain parameters or other inputs.

phpBB 2.0.17 and earlier, when the register_long_arrays directive is disabled, allows remote attackers to modify global variables and bypass security mechanisms because PHP does not define the associated HTTP_* variables.

SQL injection vulnerability in usercp_register.php in phpBB 2.0.17 allows remote attackers to execute arbitrary SQL commands via the signature_bbcode_uid parameter, which is not properly initialized.

phpBB 2.0.17 and earlier allows remote attackers to bypass protection mechanisms that deregister global variables by setting both a GET/POST/COOKIE (GPC) variable and a GLOBALS[] variable with the same name, which causes phpBB to unset the GLOBALS[] variable but not the GPC variable.