Nextcloud vulnerabilities and threats

Nextcloud Server versions 32.0.0 to before 32.0.2 and 33.0.0 to before 33.0.1 contain an improper authentication vulnerability in the files_lock app. This flaw allows authenticated users to lock or unlock files owned by other users by exploiting absolute WebDAV paths.

CVE-2026-45282 is an improper access control vulnerability in Nextcloud Server versions 32.0.0 to before 32.0.9 and 33.0.0 to before 33.0.3. An authenticated attacker who knows the share token can access attachments of link shares, bypassing password protection or download restrictions.

Nextcloud is an open source content collaboration platform. In Nextcloud Server from versions 31.0.0 to before 31.0.14, and 32.0.0 to before 32.0.4, if {lang} is used in the template directory config value, non-admin users can in some cases copy arbitrary files (depending on unix permissions) into their own Nextcloud directory via a path traversal. It is recommended that the Nextcloud Server is upgraded to 32.0.4, 31.0.14. It is recommended that the Nextcloud Enterprise Server is upgraded to 32.0.4, 31.0.14, 30.0.17.7, 29.0.17.12, 28.0.14.15

Nextcloud is an open source content collaboration platform. From version 6.1.0 to before version 8.2.2, an attacker can craft links that would redirect users to another website, when the victim uses the attackers link to log in via user OIDC. This issue has been patched in version 8.2.2.

CVE-2026-45277 is a low-severity vulnerability in Nextcloud security-advisories prior to version 2.7.2. Authenticated users could determine whether arbitrary files were linked to specific approval workflows, potentially exposing sensitive information. This issue does not allow modification or denial of service and has been addressed in Nextcloud version 2.7.2.

Nextcloud versions prior to 2.7.2 contain a privilege escalation vulnerability in the Approval app. This flaw allows users without sharing permissions to bypass authorization controls and force the system to share files with approvers. The vulnerability enables unauthorized distribution of restricted files. The issue has been addressed in Nextcloud version 2.7.2. The CVSS score is 6.5, indicating a medium severity level.

Nextcloud is an open source content collaboration platform. Prior to version 5.2.6, a missing permissions check allowed users to request reading form submissions of other users. This issue has been patched in version 5.2.6.

Nextcloud is an open source content collaboration platform. Prior to versions 21.1.10, 22.0.11, and 23.0.3, a low-privileged user can force other user's microphones to be muted in calls when no High-performance Backend is installed. This issue has been patched in versions 21.1.10, 22.0.11, and 23.0.3.

Nextcloud versions from 1.15.0 up to but not including 1.15.4, 1.16.0 up to 1.16.3, 1.17.

Nextcloud Server versions 32.0.0 to before 32.0.9 and 33.0.0 to before 33.0.3 have an improper access control vulnerability. A malicious user with access to a file share can exploit the share token to directly access chunked uploads and view temporary part files during ongoing uploads. This vulnerability could lead to unauthorized disclosure of file content during upload.

Nextcloud is an open source content collaboration platform. From versions 0.3.0 to before 3.1.0, 5.0.0 to before 5.1.0, and 6.0.0 to before 6.4.0, a missing signature verification in User OIDC allowed a malicious ID4me authority to identify as any user. This issue has been patched in versions 3.1.0, 4.1.0, 5.1.0, 6.4.0 and 8.3.0.

Nextcloud is an open source content collaboration platform. In Nextcloud Server from versions 32.0.0 to before 32.0.7 and 33.0.0 to before 33.0.1, a missing access check on API level allowed to add unknown circles by their ID directly to other circles. Since circle IDs have 62^15 complexity by default this is still unlikely to be executable at will, but if access to an ID was available via another source, memberships could be tracked like this. It is recommended that the Nextcloud Server is upgraded to 32.0.7 or 33.0.1. It is recommended that the Nextcloud Enterprise Server is upgraded to 29.0.16.14, 30.0.17.8, 31.0.14.3, 32.0.7 or 33.0.1

Nextcloud is an open source content collaboration platform. From version 2.6.0 to before version 4.3.0, when a previous collective pages was deleted and the collective was shared view-only, guests with access to the collective were able to access the deleted pages directly from the trashbin. This issue has been patched in version 4.3.0.

Nextcloud Files app versions from 33.0.0 up to but not including 33.1.0 for Android allowed bypassing the app PIN by using the back-button after unlocking a locked phone. This improper authentication vulnerability has been fixed in version 33.1.0. The issue has a medium severity with a CVSS score of 4.6.

Nextcloud is an open source content collaboration platform. From versions 17.0.0 to before 17.0.15, 18.0.0 to before 18.1.12, 19.0.0 to before 19.1.16, 20.0.0 to before 20.1.11, and 21.0.0 to before 21.0.4, a user with READ and CREATE permission, but no UPDATE permission for a team folder can rename files in the team folder. This issue has been patched in versions 17.0.15, 18.1.12, 19.1.16, 20.1.11, and 21.0.4.

Nextcloud News is an RSS/Atom feed reader. Prior to 28.3.0-beta.1, Nextcloud News allows authenticated users to add feeds by providing a feed URL (via the web interface or the API). In affected versions, an authenticated attacker could provide a URL pointing to internal/private IP ranges or localhost, causing the Nextcloud server to perform server-side HTTP requests to attacker-controlled destinations, but not relaying the result. This enables blind SSRF, which can be used to scan or probe internal network services that are reachable from the Nextcloud server. This vulnerability is fixed in 28.3.0-beta.1.

CVE-2025-66558 is a low-severity authorization bypass vulnerability in Nextcloud's Twofactor WebAuthn provider affecting versions prior to 1.4.2 and 2.4.1. The flaw arises from a missing ownership check that allows an attacker to take control of a victim's 2FA WebAuthn device by guessing a long random key string (80-128 characters). Although the attacker cannot authenticate as the victim, they can force the victim to re-register a new 2FA device upon next login, potentially disrupting user experience and 2FA integrity. The vulnerability requires remote network access, low privileges, and high attack complexity, with no user interaction needed. No known exploits are reported in the wild, and patches are available in versions 1.4.

Nextcloud talk is a video & audio conferencing app for Nextcloud. Prior to 20.1.8 and 21.1.2, a participant with chat permissions was able to delete poll drafts of other participants within the conversation based on their numeric ID. This vulnerability is fixed in 20.1.8 and 21.1.2.

Contacts app for Nextcloud easily syncs contacts from various devices with your Nextcloud and allows editing. Prior to 5.5.4, 6.0.6, and 7.2.5, a malicious user was able to modify their organisation and title field to load additional CSS files. Javascript and other options were correctly blocked by the content security policy of the Nextcloud Server code. This vulnerability is fixed in 5.5.4, 6.0.6, and 7.2.5.

Nextcloud Desktop is the desktop sync client for Nextcloud. Prior to 3.16.5, when trying to manually lock a file inside an end-to-end encrypted directory, the path of the file was sent to the server unencrypted, making it possible for administrators to see it in log files. This vulnerability is fixed in 3.16.5.