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Sun Solaris X Display Manager does not properly handle invalid XDMCP requests

Vulnerability Note VU#139504

Original Release Date: 2004-08-11 | Last Revised: 2004-08-11


There is a vulnerability in the way Sun Solaris handles invalid X Display Manager Control Protocol (XDMCP) requests. Exploitation of this vulnerability could allow an attacker to cause the X Display Manager (XDM) to crash.


The X Display Manager (xdm(1)) is responsible for managing collections of X displays from local or remote servers using the X Display Manager Control Protocol (XDMCP). The Sun Solaris X Display Manager contains a denial-of-service vulnerability that could be triggered by an invalid XDMCP packet.


A remote attacker with the ability to send XDMCP packets to a vulnerable system could cause the X Display Manager to crash.


Apply patch

Sun has issued an advisory which addresses this issue. For more information on patches available for your system, please refer to Sun Security Alert 57619.

Restrict access

Block or restrict UDP(7P) packets destined for port 177/udp from untrusted networks such as the Internet.

Disable XDMCP connections

According to the Sun Security Alert, xdm(1M) can be configured to not listen for XDMCP connections by editing the "/usr/openwin/lib/X11/xdm/xdm-config" file and adding the following line:

DisplayManager.requestPort: 0

Note: Controlling access via the access control list in the "Xaccess" file is not effective at preventing this issue.

Vendor Information


Sun Microsystems Inc. Affected

Updated:  August 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.


Please refer to Sun Security Alert 57619.

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

CVSS Metrics

Group Score Vector



This vulnerability was reported by Sun Microsystems.

This document was written by Damon Morda.

Other Information

CVE IDs: None
Severity Metric: 4.30
Date Public: 2004-08-09
Date First Published: 2004-08-11
Date Last Updated: 2004-08-11 18:39 UTC
Document Revision: 16

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