Impact
After a user received a malicious file via a share and has it synced locally or the virtual filesystem enabled, being tricked into clicking a nc://open/ link will open the default editor for the file type of the shared file, which on Windows can also sometimes mean that a file depending on the type, e.g. "vbs", is being executed.
Patches
It is recommended that the Nextcloud Desktop client is upgraded to 3.6.1
Workarounds
- Block the Nextcloud Desktop client 3.6.0 by settings the
minimum.supported.desktop.version system config to 3.6.1 on the server, so new files designed to use this attack vector are not downloaded anymore. Already existing files can still be used.
- Enforce shares to be accepted by setting the
sharing.force_share_accept system config to true on the server, so new files designed to use this attack vector are not downloaded anymore. Already existing shares can still be abused.
- Don't click malicious links
References
For more information
If you have any questions or comments about this advisory:
Impact
After a user received a malicious file via a share and has it synced locally or the virtual filesystem enabled, being tricked into clicking a nc://open/ link will open the default editor for the file type of the shared file, which on Windows can also sometimes mean that a file depending on the type, e.g. "vbs", is being executed.
Patches
It is recommended that the Nextcloud Desktop client is upgraded to 3.6.1
Workarounds
minimum.supported.desktop.versionsystem config to3.6.1on the server, so new files designed to use this attack vector are not downloaded anymore. Already existing files can still be used.sharing.force_share_acceptsystem config totrueon the server, so new files designed to use this attack vector are not downloaded anymore. Already existing shares can still be abused.References
For more information
If you have any questions or comments about this advisory: