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Citrix Java Plug-in and Microsoft ISA Server

  • CTX126693
  • Created On  Nov 04, 2010
  • Updated On  Mar 10, 2012
  • Article
  • Topic : Connectivity


After performing Form Based Authentication (FBA) to ISA (Internet Security and Acceleration) Server and connecting to an internal network, a Java client from Web Interface or Web Interface for SharePoint does not launch.

In the Java console there is an error similar to the one below:

java.lang.ClassFormatError: Incompatible magic value 1008813135 in class file com/citrix/ConnectionCenter
            at java.lang.ClassLoader.defineClass1(Native Method)
            at java.lang.ClassLoader.defineClass(Unknown Source)
            at Source)
            at sun.applet.AppletClassLoader.findClass(Unknown Source)
            at java.lang.ClassLoader.loadClass(Unknown Source)
            at sun.applet.AppletClassLoader.loadClass(Unknown Source)
            at java.lang.ClassLoader.loadClass(Unknown Source)
            at sun.applet.AppletClassLoader.loadCode(Unknown Source)
            at sun.applet.AppletPanel.createApplet(Unknown Source)
            at sun.plugin.AppletViewer.createApplet(Unknown Source)
            at sun.applet.AppletPanel.runLoader(Unknown Source)
            at Source)
            at Source)

On ISA Server there is a Deny message logged similar to the one below:

Denied Connection
Log type: Web Proxy (Reverse)
Status: 12232 The server denied the specified Uniform Resource Locator (URL). Contact the server administrator. 
Rule: RuleName
Destination: (WebInterface:443)
Request: GET http://isaserver/c50ff912-5c6b-4c13-993f-0cc27fd839f0/Clients/icajava/com/citrix/ConnectionCenter.class
Filter information: Req ID: 0f111527; Compression: client=No, server=No, compress rate=0% decompress rate=0% ; FBA cookie: exists=no, valid=no, updated=no, logged off=no, client type=unknown, user activity=yes
Protocol: https
User: anonymous
 Additional information
Client agent: Mozilla/4.0 (Windows XP 5.1) Java/1.6.0_20
Object source: (No source information is available.)
Cache info: 0x0
Processing time: 1 ms
MIME type: 


The Java Runtime Environment cannot authenticate itself to the proxy server.


A hotfix for ISA Server is available from Microsoft to address this issue:

“Applications that use an embedded Web browser program cannot access content on a Web site that you have published by using forms-based authentication in ISA Server 2006 or in Windows Essential Business Server 2008.”


Applicable Products

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