diff -r 5e7a0fedabdf -r 877f952ae2bd web/lib/Zend/Session.php
--- a/web/lib/Zend/Session.php	Thu Mar 21 17:31:31 2013 +0100
+++ b/web/lib/Zend/Session.php	Thu Mar 21 19:50:53 2013 +0100
@@ -15,9 +15,9 @@
  *
  * @category   Zend
  * @package    Zend_Session
- * @copyright  Copyright (c) 2005-2010 Zend Technologies USA Inc. (http://www.zend.com)
+ * @copyright  Copyright (c) 2005-2012 Zend Technologies USA Inc. (http://www.zend.com)
  * @license    http://framework.zend.com/license/new-bsd     New BSD License
- * @version    $Id: Session.php 22587 2010-07-16 20:14:18Z ralph $
+ * @version    $Id: Session.php 25121 2012-11-13 21:51:23Z matthew $
  * @since      Preview Release 0.2
  */
 
@@ -43,7 +43,7 @@
  *
  * @category   Zend
  * @package    Zend_Session
- * @copyright  Copyright (c) 2005-2010 Zend Technologies USA Inc. (http://www.zend.com)
+ * @copyright  Copyright (c) 2005-2012 Zend Technologies USA Inc. (http://www.zend.com)
  * @license    http://framework.zend.com/license/new-bsd     New BSD License
  */
 class Zend_Session extends Zend_Session_Abstract
@@ -308,24 +308,13 @@
                 "() before any output has been sent to the browser; output started in {$filename}/{$linenum}");
         }
 
-        if (self::$_sessionStarted && self::$_regenerateIdState <= 0) {
+        if ( !self::$_sessionStarted ) {
+            self::$_regenerateIdState = -1;
+        } else {
             if (!self::$_unitTestEnabled) {
                 session_regenerate_id(true);
             }
             self::$_regenerateIdState = 1;
-        } else {
-            /**
-             * @todo If we can detect that this requester had no session previously,
-             *       then why regenerate the id before the session has started?
-             *       Feedback wanted for:
-             //
-            if (isset($_COOKIE[session_name()]) || (!use only cookies && isset($_REQUEST[session_name()]))) {
-                self::$_regenerateIdState = 1;
-            } else {
-                self::$_regenerateIdState = -1;
-            }
-            //*/
-            self::$_regenerateIdState = -1;
         }
     }
 
@@ -335,7 +324,7 @@
      * seconds is specified, then this defaults to self::$_rememberMeSeconds.  Due to clock errors on end users' systems,
      * large values are recommended to avoid undesirable expiration of session cookies.
      *
-     * @param $seconds integer - OPTIONAL specifies TTL for cookie in seconds from present time
+     * @param int $seconds OPTIONAL specifies TTL for cookie in seconds from present time
      * @return void
      */
     public static function rememberMe($seconds = null)
@@ -394,9 +383,9 @@
      */
     public static function sessionExists()
     {
-        if (ini_get('session.use_cookies') == '1' && isset($_COOKIE[session_name()])) {
+        if ((bool)ini_get('session.use_cookies') == true && isset($_COOKIE[session_name()])) {
             return true;
-        } elseif (!empty($_REQUEST[session_name()])) {
+        } elseif ((bool)ini_get('session.use_only_cookies') == false && isset($_REQUEST[session_name()])) {
             return true;
         } elseif (self::$_unitTestEnabled) {
             return true;
@@ -426,6 +415,14 @@
      */
     public static function start($options = false)
     {
+        // Check to see if we've been passed an invalid session ID
+        if ( self::getId() && !self::_checkId(self::getId()) ) {
+            // Generate a valid, temporary replacement
+            self::setId(md5(self::getId()));
+            // Force a regenerate after session is started
+            self::$_regenerateIdState = -1;
+        }
+
         if (self::$_sessionStarted && self::$_destroyed) {
             require_once 'Zend/Session/Exception.php';
             throw new Zend_Session_Exception('The session was explicitly destroyed during this request, attempting to re-start is not allowed.');
@@ -510,6 +507,34 @@
         self::_processStartupMetadataGlobal();
     }
 
+    /**
+     * Perform a hash-bits check on the session ID
+     *
+     * @param string $id Session ID
+     * @return bool
+     */
+    protected static function _checkId($id)
+    {
+        $saveHandler = ini_get('session.save_handler');
+        if ($saveHandler == 'cluster') { // Zend Server SC, validate only after last dash
+            $dashPos = strrpos($id, '-');
+            if ($dashPos) {
+                $id = substr($id, $dashPos + 1);
+            }
+        }
+
+        $hashBitsPerChar = ini_get('session.hash_bits_per_character');
+        if (!$hashBitsPerChar) {
+            $hashBitsPerChar = 5; // the default value
+        }
+        switch($hashBitsPerChar) {
+            case 4: $pattern = '^[0-9a-f]*$'; break;
+            case 5: $pattern = '^[0-9a-v]*$'; break;
+            case 6: $pattern = '^[0-9a-zA-Z-,]*$'; break;
+        }
+        return preg_match('#'.$pattern.'#', $id);
+    }
+
 
     /**
      * _processGlobalMetadata() - this method initizes the sessions GLOBAL
@@ -572,13 +597,13 @@
                         }
                     }
                     if (empty($_SESSION['__ZF'][$namespace]['ENVGH'])) {
-                        unset($_SESSION['__ZF'][$namespace]['ENVGH']);    
+                        unset($_SESSION['__ZF'][$namespace]['ENVGH']);
                     }
                 }
-            }
-
-            if (isset($namespace) && empty($_SESSION['__ZF'][$namespace])) {
-                unset($_SESSION['__ZF'][$namespace]);
+                
+                if (isset($namespace) && empty($_SESSION['__ZF'][$namespace])) {
+                    unset($_SESSION['__ZF'][$namespace]);
+                }
             }
         }