On Wed, Oct 26, 2022 at 11:15:25AM +0100, Matt Caswell wrote:

> > I'm not promising anything. But if you send me the captures I can take a 
> > look at them.
> I've taken a look at the captures for the working and non-working scenarios.
> Do I understand correctly that your application is acting as the server 
> in this setup?
> I have compared the working and non-working captures. In both cases the 
> ClientHello is successfully received, and the server responds with a 
> ServerHello, Certificate, ServerKeyExchange and ServerHelloDone message. 
> Aside from normal variations between one session and another, AFAICT, 
> the ClientHello and the server's response messages all look identical 
> other than the server obviously has a different Certificate. The 
> Certificates themselves also look identical to each other other than the 
> subject/subjectaltname being for a different server. The intermediate 
> certs are the same in both cases.
> Following the server's ServerHelloDone the client continues with a 
> ClientKeyExchange message in the working case. In the non-working case 
> the the client immediately closes the TCP connection without sending any 
> kind of alert.

See longish thread at:


which describes a remarkably similar set of symptoms observed after a
Microsoft patch update.  Today the OP posted that a more follow-on patch
appears to have resolved the problem.

> This really looks like a problem on the client side to me.

Yes, the client just hangs up.  A known.  Disabling session tickets on
server appears to help in some cases (for no obvious reason).  Applying
the follow-on update is a better solution if applicable.


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