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).

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

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

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.

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

• Updated Contributing Factors and Resolution sections

• Updated Contributing Factors and Resolution sections

• Updated Contributing Factors and Resolution sections

• State: Resolved
• Updated Contributing Factors and Resolution sections

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