Vncviewer 1.8.2.4 crashes in combination with Linux Mint x11vnc

[paulratcliffe-cpu]

Vncviewer application crashes about 17 seconds after connecting to the server, regardless of activity or not. Perfectly repeatable.

Faulting module name: ntdll.dll, version: 10.0.19041.7291, time stamp: 0xba81a27d
Exception code: 0xc0000374
Fault offset: 0x00000000000ff549
Faulting process ID: 0x6654
Faulting application start time: 0x01dd131354266dde
Faulting application path: C:\Program Files\uvnc bvba\UltraVNC\vncviewer.exe
Faulting module path: C:\Windows\SYSTEM32\ntdll.dll
Report ID: 3f97f72e-78d1-4644-8920-10249808c419
Faulting package full name: 
Faulting package-relative application ID: 

0xc0000374 is apparently a heap corruption error. I guess you can work out the source line from the Fault offset.
Log file attached.

Client is W10 22H2 with extended service updates, fully patched.
Server is Linux Mint x11vnc via SSH tunnel.

vncviewer.txt

[RamogninoF]

I'm hitting what looks like the same crash — same version, same exception, same
general setup (UltraVNC Viewer client on Windows, x11vnc server on Linux Mint,
connection via SSH tunnel) — but with a different, also perfectly repeatable,
trigger: holding the left mouse button and dragging on the remote screen
(e.g. selecting text) crashes the viewer every time, regardless of how long the
session has been open. No 17-second idle delay on my end — it's the drag
itself that does it.

Environment:

• UltraVNC Viewer 1.8.2.4
• Client: Windows 11 (Windows 10.0.26100), fully patched
• Server: Linux Mint, x11vnc, connected through an SSH tunnel (same shape as OP's setup)

Windows Event Viewer, Application log (Event ID 1000):

Faulting application name: vncviewer.exe, version: 1.8.2.4, time stamp: 0x6a2f194b
Faulting module name: ntdll.dll, version: 10.0.26100.8875, time stamp: 0xba65e4a2
Exception code: 0xc0000374
Fault offset: 0x0000000000112165
Faulting process id: 0x18E90
Faulting application path: C:\Program Files\uvnc bvba\UltraVNC\vncviewer.exe
Faulting module path: C:\WINDOWS\SYSTEM32\ntdll.dll

Same exception code (0xC0000374 / STATUS_HEAP_CORRUPTION) and faulting
module as the original report, but a different fault offset and a clearly
different trigger (input-driven vs. time-based/idle). Could be the same
underlying heap corruption surfacing on two different code paths — flagging
here in case correlating the two offsets/triggers helps narrow down the
source. Happy to enable verbose viewer logging and share output if useful.

[paulratcliffe-cpu]

I've revisited this having found that the repeatable problem only happened sometimes - when it happened, it happened repeatedly, but when it didn't it was perfectly OK on every occasion. So it seems like it was something environmental, and the obvious thing is the clipboard.
Having reviewed the changes since 1.8.2.4, I see there was a fix for a clipboard problem, so I found the 1.8.2.5-dev version, installed the viewer from that, and the problem has gone away for me.

I can't reproduce the left click/drag problem with either version.

[RamogninoF]

I noticed that using "Preemptive Updates" seems to limit the occurrence of the crash, but still happening from time to time. Otherwise it is fairly impossible to select text for more then a minute or so. Unfortunately I cannot help in tracing down the problem

[Neustradamus]

@paulratcliffe-cpu, @RamogninoF: Thanks for your feedback!

@paulratcliffe-cpu: With 1.8.2.5-dev, the problem has completely disappeared?

@RamogninoF: Can you try the 1.8.2.5-dev build?

[paulratcliffe-cpu]

With 1.8.2.5-dev, the problem has completely disappeared?

Yes, at least I can't provoke like I can with .4