Public Vulnerability Reports

Macromedia JRun 4 mod_jrun Apache Module Buffer Overflow Vulnerability



Macromedia JRun 4 is a full Java 2 Enterprise Edition (J2EE) compatible
application server.

Further details are available at:


Remote exploitation of a buffer overflow vulnerability in Macromedia's
JRun 4 mod_jrun Apache module could allow execution of arbitrary code.

The problem specifically exists in the WriteToLog function of mod_jrun
and mod_jrun20, where a fixed size buffer is allocated on the stack. No
bounds checking is performed on the input. When the Verbose logging
option is set, this function may be called with user-supplied data. If
this data is longer than the space which has been allocated, a buffer
overflow may occur. Specially formed input may allow execution of
arbitrary commands.


Successful exploitation allows execution of arbitrary code with the
permissions of the user of the httpd process, typically 'nobody' or

As the Verbose option is not set by default, most installs will not be
vulnerable. An overly long Content-Type field, among other header
fields, can be used to trigger this buffer overflow.


iDEFENSE has confirmed that JRun 4.0 SP1a is vulnerable on Apache httpd
1.3.x and 2.0.x platforms. It is suspected that all versions of mod_jrun
are currently affected.



Setting the Verbose option to "false" in the httpd.conf will prevent
this vulnerability from being exploitable. After editing the httpd.conf,
restart the httpd. This will reduce the amount of data logged by the
server, but will prevent exploitation of this vulnerability.


MPSB04-08 - Cumulative Security Patch available for JRun server


The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CAN-2004-0646 to this issue. This is a candidate for inclusion in
the CVE list (, which standardizes names for
security problems.


06/18/2004   iDEFENSE Clients notified
06/18/2004   Initial vendor notification
06/18/2004   Initial vendor response
09/29/2004   Public disclosure


The discoverer wishes to remain anonymous.

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Copyright © 2004 Verisign, Inc.

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