Untrusted Search Path in Nextcloud Desktop Client

Description

Impact

The Nextcloud Desktop Client invokes its uninstaller script when being installed to make sure there are no remnants of previous installations.

The Client did however search the Uninstall.exe file in a folder that can be written by regular users. This could lead to a case where a malicious user created a malicious Uninstall.exe, which would be executed with administrative privileges on the Nextcloud Desktop Client installation.

Patches

It is recommended that the Nextcloud Desktop client is upgraded to 3.3.0.

Workarounds

Do not allow untrusted users to create content in the C:\ system folder. Verify that there’s no malicious C:\Uninstall.exe file on the system.

References

• HackerOne
• Pull Request

For more information

If you have any questions or comments about this advisory:

• Create a post in nextcloud/security-advisories
• Customers: Open a support ticket at support.nextcloud.com