MPSB05-05 - Security Patch available for JRun 4.0 token collision

14 july, 2005

Summary

Under high load, JRun may generate two sessions with the same authentication token. This cannot be controlled by an attacker and it occurs very rarely, but it may cause two authenticated users to share information from a single user session.

Solution

Macromedia has released a JRun 4.0 patch that can be downloaded and applied.  This only affects products based on the JRun 4 server (listed below). 

• Download JRun 4.0 patch (ZIP, 9 KB)

Affected Software Versions

• ColdFusion MX 7.0 Enterprise Multi-Server Edition
• ColdFusion MX 7.0 Enterprise
• ColdFusion MX 6.1 Enterprise
• J2EE Configuration – ColdFusion MX 6.1 for JRun 4
• JRun 4.0

NOTE: ColdFusion MX 6.1 and 7.0 Standard editions are not affected.

Severity Rating

Macromedia categorizes this issue as a moderate issue and recommends users immediately evaluate their configuration.

Details

When a user is authenticated, JRun generates an internal authentication token to track a user's information (principal, credentials, etc.).  Under load, it's possible two users can obtain the same token number and shared session information. Macromedia has received a report of this occurring in a production system, but it happens very infrequently, and there is no way for an attacker to cause or control a collision.

The patch modifies the authentication token generation algorithm to prevent generation of duplicate tokens.

Making the Changes

NOTE: Back up your existing files before making changes. As always, test the changes in a non-production environment before applying the changes to production servers.

JRun 4.0 or ColdFusion MX 7.0 Multi-Server Edition

1. Download the patch above and expand it.
2. Stop all JRun servers.
3. Place the jrun-hotfix-MPSB05-05.jar in the {jrun_root}/servers/lib directory.
4. Restart JRun.

ColdFusion MX 7.0 Enterprise or ColdFusion MX 6.1 Enterprise Edition

(For ColdFusion 6.1, Updater 1 is required)

1. Download the patch above and expand it.
2. Stop ColdFusion MX.
3.  Place the jrun-hotfix-MPSB05-05.jar in the {cf_root}/runtime/servers/lib directory.
4.  (Create the {cf_root}/runtime/servers/lib directory if it does not exist.) 

On Unix systems only:

1. Edit the file {cf_root}/runtime/bin/jvm.config
2. Find the JVM classpath section
3. Add {application.home}/runtime/servers/lib as the first entry in the java.class.path list

   Example: JVM classpath

   java.class.path={application.home}/runtime/servers/lib,{application.home}/runtime/../../src,{application.home}/lib/cfusion.jar,{application.home}/runtime/lib/webservices.jar

4. Start ColdFusion MX

NOTE: This patch will be incorporated into ColdFusion MX 7.0 Updater 1 and JRun 4.0 Updater 6.

Acknowledgements

Macromedia would like to thank Greg Ball from the University of Virginia for reporting this vulnerability and for working with us to help protect our customers' security

Revisions

July 28, 2005 — Bulletin amended.
July 14, 2005 — Bulletin first created.

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