#101549: X Display Manager (xdm(1)) May Crash Due to Invalid XDMCP Request (formerly Document ID: 57619)

Sun(sm) Alert Notification

Sun Alert ID: 101549 (formerly 57619)
Synopsis: X Display Manager (xdm(1)) May Crash Due to Invalid XDMCP Request
Category: Security
Product: Solaris 9 Operating System, Solaris 7 Operating System, Solaris 8 Operating System
BugIDs: 5023755
Avoidance: Workaround, Patch
State: Resolved
Date Released: 09-Aug-2004, 01-Dec-2005
Date Closed: 01-Dec-2005
Date Modified: 13-Oct-2004, 07-Oct-2004, 30-Nov-2005, 01-Dec-2005

1. Impact

A remote unprivileged user may be able to crash the X Display Manager (xdm(1)) when using an invalid X Display Manager Control Protocol (XDMCP) request, thus causing a Denial of Service (DoS).

2. Contributing Factors

This issue can occur in the following releases:

SPARC Platform

Solaris 7 without patch 108376-46
Solaris 8 without patch 111844-03
Solaris 9 without patch 112785-38

x86 Platform

Solaris 7 without patch 108377-41
Solaris 8 without patch 111845-03
Solaris 9 without patch 112786-27

3. Symptoms

If the described issue occurs, the X Display Manager will exit without warning.

Solution Summary

Top

4. Relief/Workaround

To reduce the possibility of the described issue from occurring, network administrators should block UDP(7P) packets to port 177 across any firewall where XDMCP remote session service is not required.

If XDMCP remote session access to a machine is not required at all, but graphical login access via xdm(1M) for console devices is required, 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.

5. Resolution

This issue is addressed in the following releases:

SPARC Platform

Solaris 7 with patch 108376-46 or later
Solaris 8 with patch 111844-03 or later
Solaris 9 with patch 112785-38 or later

x86 Platform

Solaris 7 with patch 108377-41 or later
Solaris 8 with patch 111845-03 or later
Solaris 9 with patch 112786-27 or later

Change History

13-Oct-2004:

Updated Contributing Factors and Resolution sections

07-Oct-2004:

Updated Contributing Factors and Resolution sections

30-Nov-2005:

Updated Contributing Factors and Resolution sections

01-Dec-2005:

State: Resolved
Updated Contributing Factors and Resolution sections

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