WinVNC on Windows 2000 Professional crashes when client connects

Bruce Lilly blilly "at"
Wed, 13 Jun 2001 20:00:35 +0000

Note that it is the machine running WinVNC (as a service) which
crashes (immediate reboot), not the client running VNCviewer.

I've had this problem intermittently over several versions of WinVNC
and all service packs for Windows 2000 and on a couple of hardware

The crash occurs immediately after the client tries to connect,
before the client can pop up the password window.

I suspect that part of the fault may lie in the VNCviewer client,
as making some seemingly irrelevant changes there often affects
whether or not the server crashes; I suspect that something that
the client sends to the WinVNC server causes the latter to crash
the OS (also, the server tends to crash when the VNC port is scanned
by security software looking for open TCP ports).

As an example of a change that affects crashing, recently I had a
situation where connecting from one machine to another caused the
machine running WinVNC to crash. It happened repeatably, every time.
Connecting from a different client didn't cause the crash.  The
only difference between the two was that the client which caused
the server to crash was using a FQDN (specifically, "")
for the connection to the server, while the client that didn't cause
the server to crash used a nickname ("bog:0").  I changed the other
client to also use the nickname, and I've now connected to the server
from that client at least a half dozen times with no crash. (later,
it crashed again).

I have enabled full logging on one of the WinVNC servers in the hope
that there may be something informative written prior to a crash.
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