search menu icon-carat-right cmu-wordmark

CERT Coordination Center

Macromedia JRun Server insecurely generates and handles JSESSIONIDs

Vulnerability Note VU#584958

Original Release Date: 2004-10-12 | Last Revised: 2004-10-12


A vulnerability exists in Macromedia JRun that may allow an attacker to gain access to an authenticated user's session.


Macromedia JRun is an application server that works with most popular web servers such as Apache and IIS. Macromedia states that JRun is deployed at over 10,000 organizations worldwide. The JSESSIONID is a string that uniquely identifies a user's session. JSESSIONIDs are generated using a limited character set (0-9) , therefore reducing the search space required for a brute-force attack. According to reports, JRun Server also handles the JSESSIONIDs insecurely potentially allowing an attacker to gain access to an authorized user's session. The insecure handling may involve how JSESSIONIDs are stored in web browser cookies or URLs. However, the specific details are not available at this time.


Exploitation of this vulnerability may allow an attacker to hijack an authenticated user's session allowing the attacker to access sensitive information or execute commands on the server with the privileges of the compromised session.


Apply Patch

In the latest updater increases the security of the JSESSIONID by expanding the character set used for JESSIONIDs to include letters as well as numbers.

It is available for download at:

Vendor Information


Macromedia Inc. Affected

Notified:  September 29, 2004 Updated: October 11, 2004



Vendor Statement

We have not received a statement from the vendor.

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.


The CERT/CC has no additional comments at this time.

If you have feedback, comments, or additional information about this vulnerability, please send us email.

CVSS Metrics

Group Score Vector



This vulnerability was reported in Macromedia Security Bulletin MPSB04-08.Macromedia credits @Stake for helping to discover and report this issue.

This document was written by Jeff Gennari.

Other Information

CVE IDs: None
Severity Metric: 5.32
Date Public: 2004-09-23
Date First Published: 2004-10-12
Date Last Updated: 2004-10-12 16:52 UTC
Document Revision: 124

Sponsored by CISA.