CVE-2026-90928

A vulnerability in File Browser before version 2.63.16 allows an authenticated user with Create and Modify permissions to create attacker-controlled files outside the user's scope. The issue arises because ScopedFs validates the nearest existing ancestor of a dangling symlink as in scope and then follows the symlink during file creation.

File Browser is a file management interface that, starting from version 2.0.0-rc.1, allows unauthenticated attackers to impersonate users, including admins, by sending a forged HTTP header. No credentials are required to gain access.

File Browser prior to version 2.63.6 had a vulnerability in the Hook Authentication feature that allowed delegating login verification to an external shell command. User-supplied credentials were interpolated into this command string without sanitization, enabling remote attackers to execute arbitrary OS commands before any authentication.

File Browser through 2.63.23 applies path rules to the requested lexical path but resolves symbolic links without reapplying rules to the target, allowing authenticated users to bypass deny rules. Attackers can read and overwrite rule-denied files by accessing them through in-scope symbolic link aliases that resolve to denied paths.

File Browser versions >= 2.5.0 and <= 2.63.23 contain an incorrect authorization flaw in the direct-upload endpoint (resourcePostHandler in http/resource.go). Unlike the TUS upload handler, the direct-upload handler does not reject a target that is an existing directory; a POST with ?override=true aimed at a directory fails inside writeFile and the failure-cleanup path calls Fs.RemoveAll on the request path, recursively deleting the entire tree. This cleanup is not gated by Perm.Delete or the checkDescendants rule, so an authenticated non-administrator with default Create and Modify permissions can delete directories they are not authorized to delete.

File Browser versions from 2.63.6 through 2.63.23 fail to clean up public share links when a privileged user deletes another user's shared file. Attackers can access the surviving share link to retrieve new unrelated content uploaded to the same path without authentication.

File Browser prior to 2.63.17 directly serializes the Link storage struct in sharePostHandler, shareListHandler, and shareGetsHandler, exposing password_hash and the bypass token in API responses. An administrator can retrieve these secrets for every user's shares, enabling offline password cracking and direct access to protected shares.

File Browser versions before 2.63.20 fail to honor the createUserDir isolation in proxy and hook authentication auto-provisioning paths. Attackers with valid upstream-authenticated credentials can read, modify, delete, and share files belonging to other users by exploiting the server root scope assignment.

File Browser before v2.63.22 fails to validate access rules for descendants during recursive copy, rename, and delete operations, allowing authenticated users to bypass path-based access controls. Attackers can copy, rename, or delete denied files by operating on their allowed parent directory, defeating rule-based isolation for confidentiality and integrity.

File Browser versions from 2.50.0 through 2.63.21 fail to validate JWT expiration when proxy authentication is configured with a non-default logout page. Attackers with a previously valid token can access protected routes and administrative endpoints indefinitely, and exchange expired tokens for fresh ones via the renewal endpoint.