Nextcloud Server — набор клиент-серверных программ для создания и использования хранилища данных.

Nextcloud Server before 9.0.54 and 10.0.0 suffers from an improper authorization check on removing shares. The Sharing Backend as implemented in Nextcloud does differentiate between shares to users and groups. In case of a received group share, users should be able to unshare the file to themselves but not to the whole group. The previous API implementation simply unshared the file to all users in the group.

Nextcloud Server before 9.0.54 and 10.0.1 & ownCloud Server before 9.0.6 and 9.1.2 suffer from content spoofing in the dav app. The exception message displayed on the DAV endpoints contained partially user-controllable input leading to a potential misrepresentation of information.

Nextcloud Server before 9.0.52 & ownCloud Server before 9.0.4 are not properly verifying restore privileges when restoring a file. The restore capability of Nextcloud/ownCloud was not verifying whether a user has only read-only access to a share. Thus a user with read-only access was able to restore old versions.

Nextcloud Server before 9.0.55 and 10.0.2 suffers from a permission increase on re-sharing via OCS API issue. A permission related issue within the OCS sharing API allowed an authenticated adversary to reshare shared files with an increasing permission set. This may allow an attacker to edit files in a share despite having only a 'read' permission set. Note that this only affects folders and files that the adversary has at least read-only permissions for.

Nextcloud Server before 9.0.55 and 10.0.2 suffers from a bypass in the quota limitation. Due to not properly sanitizing values provided by the `OC-Total-Length` HTTP header an authenticated adversary may be able to exceed their configured user quota. Thus using more space than allowed by the administrator.

Nextcloud Server before 11.0.3 is vulnerable to disclosure of valid share tokens for public calendars due to a logical error. Thus granting an attacker potentially access to publicly shared calendars without knowing the share token.

Nextcloud Server before 9.0.55 and 10.0.2 suffers from a Denial of Service attack. Due to an error in the application logic an authenticated adversary may trigger an endless recursion in the application leading to a potential Denial of Service.

Nextcloud Server before 9.0.55 and 10.0.2 suffers from a error message disclosing existence of file in write-only share. Due to an error in the application logic an adversary with access to a write-only share may enumerate the names of existing files and subfolders by comparing the exception messages.

Nextcloud Server before 10.0.4 and 11.0.2 are vulnerable to disclosure of calendar and addressbook names to other logged-in users. Note that no actual content of the calendar and addressbook has been disclosed.

Nextcloud Server before 9.0.55 and 10.0.2 suffers from a creation of folders in read-only folders despite lacking permissions issue. Due to a logical error in the file caching layer an authenticated adversary is able to create empty folders inside a shared folder. Note that this only affects folders and files that the adversary has at least read-only permissions for.