diff --git a/Apache/SOGo-debian.conf b/Apache/SOGo-debian.conf
index 5490b5248..aced3f41a 100644
--- a/Apache/SOGo-debian.conf
+++ b/Apache/SOGo-debian.conf
@@ -29,6 +29,16 @@ AliasMatch /SOGo/so/ControlPanel/Products/(.*)/Resources/(.*) \
 ProxyRequests Off
 SetEnv proxy-nokeepalive 1
 ProxyPreserveHost On
+
+# When using CAS, you should uncomment this and install cas-proxy-validate.py
+# in /usr/lib/cgi-bin to reduce server overloading
+#
+# ProxyPass /SOGo/casProxy http://localhost/cgi-bin/cas-proxy-validate.py
+# <Proxy http://localhost/app/cas-proxy-validate.py>
+#   Order deny,allow
+#   Allow from your-cas-host-addr
+# </Proxy>
+
 ProxyPass /SOGo http://127.0.0.1:20000/SOGo retry=0
 
 <Proxy http://127.0.0.1:20000/SOGo>
diff --git a/Apache/SOGo.conf b/Apache/SOGo.conf
index 4be65695b..d1d26fa81 100644
--- a/Apache/SOGo.conf
+++ b/Apache/SOGo.conf
@@ -23,6 +23,16 @@ AliasMatch /SOGo/so/ControlPanel/Products/(.*)/Resources/(.*) \
 ProxyRequests Off
 SetEnv proxy-nokeepalive 1
 ProxyPreserveHost On
+
+# When using CAS, you should uncomment this and install cas-proxy-validate.py
+# in /usr/lib/cgi-bin to reduce server overloading
+#
+# ProxyPass /SOGo/casProxy http://localhost/cgi-bin/cas-proxy-validate.py
+# <Proxy http://localhost/app/cas-proxy-validate.py>
+#   Order deny,allow
+#   Allow from your-cas-host-addr
+# </Proxy>
+
 ProxyPass /SOGo http://127.0.0.1:20000/SOGo retry=0
 
 <Proxy http://127.0.0.1:20000/SOGo>
diff --git a/ChangeLog b/ChangeLog
index 2ceba8289..02d616b3f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2010-10-12  Wolfgang Sourdeau  <wsourdeau@inverse.ca>
+
+	* Scripts/cas-proxy-validate.py: new script that resolve
+	reentrancy issues occurring when using SOGo in CAS mode, when SOGo
+	requests a PGT from the CAS server.
+
 2010-10-11  Wolfgang Sourdeau  <wsourdeau@inverse.ca>
 
 	* UI/WebServerResources/UIxAttendeesEditor.js:
diff --git a/Scripts/cas-proxy-validate.py b/Scripts/cas-proxy-validate.py
new file mode 100755
index 000000000..96bd6b59d
--- /dev/null
+++ b/Scripts/cas-proxy-validate.py
@@ -0,0 +1,88 @@
+#!/usr/bin/python
+# cas-proxy-validate.py - this file is part of SOGo
+#
+#  Copyright (C) 2010 Inverse inc.
+#
+# Author: Wolfgang Sourdeau <wsourdeau@inverse.ca>
+#
+# This file is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2, or (at your option)
+# any later version.
+#
+# This file is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; see the file COPYING.  If not, write to
+# the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+# Boston, MA 02111-1307, USA.
+
+# This script provides a CGI to avoid reentrancy issues when using SOGo in CAS
+# mode
+
+# debian dep: python-memcache
+
+import cgi
+import memcache
+import os
+import sys
+
+config = { "cas-addr": "127.0.0.1",
+           "memcached-addrs": ["127.0.0.1:11211"] }
+
+class CASProxyValidator:
+    def run(self):
+        if os.environ.has_key("GATEWAY_INTERFACE"):
+            self._runAsCGI()
+        else:
+            self._runAsCmd()
+
+    def _runAsCGI(self):
+        if self._cgiChecks():
+            form = cgi.FieldStorage()
+            if form.has_key("pgtId") and form.has_key("pgtIou"):
+                pgtIou = form.getfirst("pgtIou")
+                pgtId = form.getfirst("pgtId")
+                self._registerPGTIdAndIou(pgtIou, pgtId)
+                message = "'%s' set to '%s'" \
+                          % ("cas-pgtiou:%s" % pgtIou, pgtId)
+                self._printCGIError(message, 200)
+            else:
+                self._printCGIError("Missing parameter.")
+
+    def _cgiChecks(self):
+        rc = False
+
+        if os.environ["REQUEST_METHOD"] == "GET":
+            if os.environ["REMOTE_ADDR"] == config["cas-addr"]:
+                rc = True
+            else:
+                self._printCGIError("Who are you? (%s)" % os.environ["REMOTE_ADDR"])
+        else:
+            self._printCGIError("Only 'GET' is accepted.")
+
+        return rc
+
+    def _printCGIError(self, message, code = 403):
+        print("Status: %d\n"
+              "Content-Type: text/plain; charset=utf-8\n\n%s"
+              % (code, message))
+
+    def _runAsCmd(self):
+        if len(sys.argv) == 3:
+            self._registerPGTIdAndIou(sys.argv[1], sys.argv[2])
+            print "set '%s' to '%s'" \
+                  % ("cas-pgtiou:%s" % sys.argv[1], sys.argv[2])
+        else:
+            raise Exception, "Missing or too many parameters."
+
+    def _registerPGTIdAndIou(self, pgtIou, pgtId):
+        mc = memcache.Client(config["memcached-addrs"])
+        mc.set("cas-pgtiou:%s" % pgtIou, pgtId)
+
+if __name__ == "__main__":
+    process = CASProxyValidator()
+    process.run()