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Old 11-25-2019, 06:33 PM
dverbern dverbern is offline
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Join Date: Mar 2019
Posts: 31
Unhappy Cannot negotiate KEX with 3rd party - "No appropriate prime between 1024 and 1024"


Using VShell 4.4.3 (x64 build 1966), a 3rd party is failing to connect to VShell - seems to be failing during KEX whereby "diffie-hellman-group-exchange-sha256" is selected, but then logs show error:

"The transport was aborted with a disconnect packet: No appropriate prime between 1024 and 1024 is available."

This issue appears to have been occurring for some time, and may date to when I had upgraded our VShell version - but this is the first I'm hearing of this issue from this particular 3rd party.

VShell currently has the following Key Exchange Algorithms checked:


I can indeed see a 'primes.txt' file within the VShell directory on our server, but not sure what to make of its contents.

Can someone please assist me in overcoming this issue?
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Old 11-26-2019, 07:52 AM
bgagnon bgagnon is offline
VanDyke Technical Support
Join Date: Oct 2008
Posts: 4,636
Hi dverbern,

As a note, especially for VShell issues, it is preferred you contact support@vandyke.com directly. Working these issues in the forums involves a lot of overhead.

For this issue specifically, please contact us at the above email (Attn: Forum Thread #13985) as it is related to an intentional change in VShell as of v4.1.1.

VanDyke Software
Technical Support
(505) 332-5730

Last edited by jdev; 06-21-2022 at 02:29 PM.
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kex , primes

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