Nextcloud: 3D Viewer authentication bypass (CVE-2026-104189)

Nextcloud 3D Viewer versions 1.7.9 through 3.3.1 contain an authentication bypass vulnerability (CVE-2026-104189) in the PublicFileController. The application fails to enforce share password requirements because the controller does not correctly implement OCP\AppFramework\PublicShareController, causing PublicShareMiddleware to skip authorization checks. Attackers with a known share token can access 3D files (such as STL, GLB/glTF, OBJ, STEP, and IFC) within password-protected links without providing the password. This issue is resolved in version 3.3.2.

Impact

Successful exploitation allows unauthorized access to and exfiltration of 3D model files protected by password-restricted share links. Only 3D file formats supported by the application are affected.

Recommendation

• Upgrade the 3D Viewer for Nextcloud to version 3.3.2 or later immediately.
• If upgrading is not immediately feasible, disable the 3D Viewer application using the command: occ app:disable threedviewer.
• Avoid relying on password protection for public shares containing sensitive 3D model files until the patch is applied.