[Bug]: External Storage sftp no matching key exchange methods found #53867
Description
⚠️ This issue respects the following points: ⚠️
- This is a bug, not a question or a configuration/webserver/proxy issue.
- This issue is not already reported on Github OR Nextcloud Community Forum (I've searched it).
- Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
- I agree to follow Nextcloud's Code of Conduct.
Bug description
When trying to connect Nextcloud external storage via sftp to an up-to-date OpenSSH Server on Arch Linux (OpenSSH_10.0p2, OpenSSL 3.5.1 1 Jul 2025), it won't work because of no matching key echange method found.
Error message in the systems journal:
no matching key exchange method found. Their offer: diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1,ext-info-c,kex-strict-c-v00@openssh.com [preauth]
Steps to reproduce
- Activate Nextcloud external Storage App
- try to connect to an up-to-date openssh server via sftp (arch linux)
- it will fail, check logs of linux machine for "no matching key exchange method found" line
Expected behavior
External Storage App should be able to connect to an up-to-date openssh-server, so key exchange methods should be up-to-date in the app.
Nextcloud Server version
31
Operating system
Other
PHP engine version
PHP 8.4
Web server
Apache (supported)
Database engine version
MariaDB
Is this bug present after an update or on a fresh install?
None
Are you using the Nextcloud Server Encryption module?
Encryption is Disabled
What user-backends are you using?
- Default user-backend (database)
- LDAP/ Active Directory
- SSO - SAML
- Other
Configuration report
{
"system": {
"instanceid": "***REMOVED SENSITIVE VALUE***",
"passwordsalt": "***REMOVED SENSITIVE VALUE***",
"secret": "***REMOVED SENSITIVE VALUE***",
"trusted_domains": [
"***REMOVED SENSITIVE VALUE***"
],
"datadirectory": "***REMOVED SENSITIVE VALUE***",
"overwrite.cli.url": "https:\/\/***REMOVED SENSITIVE VALUE***",
"htaccess.RewriteBase": "\/",
"dbtype": "mysql",
"version": "31.0.6.2",
"dbname": "***REMOVED SENSITIVE VALUE***",
"dbhost": "***REMOVED SENSITIVE VALUE***",
"dbtableprefix": "oc_",
"dbuser": "***REMOVED SENSITIVE VALUE***",
"dbpassword": "***REMOVED SENSITIVE VALUE***",
"logtimezone": "UTC",
"installed": true,
"mail_from_address": "***REMOVED SENSITIVE VALUE***",
"mail_smtpmode": "smtp",
"mail_domain": "***REMOVED SENSITIVE VALUE***",
"maintenance": false,
"loglevel": 0,
"mail_smtpauthtype": "PLAIN",
"mail_smtpauth": 1,
"mail_smtphost": "***REMOVED SENSITIVE VALUE***",
"mail_smtpname": "***REMOVED SENSITIVE VALUE***",
"mail_smtppassword": "***REMOVED SENSITIVE VALUE***",
"theme": "",
"mysql.utf8mb4": true,
"memcache.local": "\\OC\\Memcache\\APCu",
"updater.release.channel": "stable",
"default_phone_region": "DE",
"mail_sendmailmode": "smtp",
"mail_smtpport": "25",
"app_install_overwrite": [
"news",
"files_texteditor"
]
}
}List of activated Apps
Enabled:
- activity: 4.0.0
- admin_audit: 1.21.0
- app_api: 5.0.2
- audioplayer: 3.4.1
- bookmarks: 15.1.1
- bruteforcesettings: 4.0.0
- calendar: 5.3.4
- circles: 31.0.0
- cloud_federation_api: 1.14.0
- comments: 1.21.0
- contacts: 7.1.4
- contactsinteraction: 1.12.0
- dav: 1.33.0
- deck: 1.15.1
- federatedfilesharing: 1.21.0
- federation: 1.21.0
- files: 2.3.1
- files_downloadlimit: 4.0.0
- files_external: 1.23.0
- files_pdfviewer: 4.0.0
- files_reminders: 1.4.0
- files_sharing: 1.23.1
- files_texteditor: 2.15.1
- files_trashbin: 1.21.0
- files_versions: 1.24.0
- impersonate: 2.0.0
- keeweb: 0.6.21
- logreader: 4.0.0
- lookup_server_connector: 1.19.0
- news: 26.0.2
- notes: 4.12.1
- notifications: 4.0.0
- oauth2: 1.19.1
- password_policy: 3.0.0
- photos: 4.0.0-dev.1
- privacy: 3.0.0
- profile: 1.0.0
- provisioning_api: 1.21.0
- recognize: 9.0.3
- related_resources: 2.0.0
- richdocuments: 8.7.1
- serverinfo: 3.0.0
- settings: 1.14.0
- sharebymail: 1.21.0
- spreed: 21.1.1
- systemtags: 1.21.1
- tasks: 0.16.1
- text: 5.0.0
- theming: 2.6.1
- twofactor_backupcodes: 1.20.0
- twofactor_totp: 13.0.0-dev.0
- updatenotification: 1.21.0
- viewer: 4.0.0
- webhook_listeners: 1.2.0
- workflowengine: 2.13.0
Disabled:
- apporder: 0.15.0 (installed 0.15.0)
- dashboard: 7.11.0 (installed 7.0.0)
- encryption: 2.19.0
- files_rightclick: 0.15.1 (installed 1.6.0)
- firstrunwizard: 4.0.0 (installed 2.1)
- keeporsweep: 0.3.0 (installed 0.3.0)
- nextcloud_announcements: 3.0.0 (installed 1.1)
- recommendations: 4.0.0 (installed 1.0.0)
- support: 3.0.0 (installed 1.3.0)
- survey_client: 3.0.0 (installed 0.1.5)
- suspicious_login: 9.0.1
- twofactor_admin: 4.8.0 (installed 4.8.0)
- twofactor_gateway: 0.20.0 (installed 0.20.0)
- twofactor_nextcloud_notification: 5.0.0
- user_ldap: 1.22.0
- user_status: 1.11.0 (installed 1.0.1)
- weather_status: 1.11.0 (installed 1.0.0)Nextcloud Signing status
No errors have been found.Nextcloud Logs
{"reqId":"wGvVXpOUjohVbqyMVVD0","level":1,"time":"2025-07-08T12:30:43+00:00","remoteAddr":"**REMOVED SENSITIVE VALUE***","user":"**REMOVED SENSITIVE VALUE***","app":"PHP","method":"GET","url":"/apps/files_external/userglobalstorages/1?testOnly=true","message":"No compatible key exchange algorithms found at /var/www/**REMOVED SENSITIVE VALUE***/3rdparty/phpseclib/phpseclib/phpseclib/Net/SSH2.php#1757","userAgent":"Mozilla/5.0 (X11; Linux x86_64; rv:139.0) Gecko/20100101 Firefox/139.0","version":"31.0.6.2","data":{"app":"PHP"},"id":"686d141f54115"}Additional info
No response