Unable to exchange encryption keys

From: Werner Stolz via curl-users <curl-users_at_lists.haxx.se>
Date: Mon, 24 Nov 2025 14:53:05 +0000

We have recently upgraded our version of curl because we are encountering more and more cases of being unable to establish connections
due to deprecated ciphers.

We first encountered this error in 2022, and the only suggestion was to upgrade our version of curl. We have now done that, and the problem
actually seems WORSE.

Here is our version of curl.

curl --version
curl 8.14.1 (powerpc-ibm-aix7.1.5.0) libcurl/8.14.1 OpenSSL/3.0.10 zlib/1.2.13 libssh2/1.11.1 nghttp2/1.62.1 OpenLDAP/2.5.16
Release-Date: 2025-06-04
Protocols: dict file ftp ftps gopher gophers http https imap imaps ipfs ipns ldap ldaps mqtt pop3 pop3s rtsp scp sftp smb smbs smtp smtps telnet tftp ws wss
Features: alt-svc AsynchDNS GSS-API HSTS HTTP2 HTTPS-proxy IPv6 Kerberos Largefile libz NTLM SPNEGO SSL threadsafe UnixSockets

Here is the error message that we are getting. I have removed all the identifying information.

curl -k -v sftp://url.com:22/ --user 'USER:PASSWORD'
* Host url.com:22 was resolved.
* IPv6: (none)
* IPv4: octet.octet.octet.octet, 18.222.41.6
* Trying octet.octet.octet.octet:22...
* Connected to io.envestnet.com (octet.octet.octet.octet) port 22
* libssh2 cryptography backend: openssl compatible
* User: USER
* Failure establishing ssh session: -5, Unable to exchange encryption keys
* closing connection #0
curl: (2) Failure establishing ssh session: -5, Unable to exchange encryption keys





Werner Stolz
Advisor, Senior Software Developer
Office: 848.305.7158
Mobile: 630.404.3815
Chicago
InvestCloud.com<https://www.investcloud.com/> | LinkedIn<https://www.linkedin.com/company/investcloud/>

CNBC World's Top Fintech Companies 2024


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Received on 2025-11-24