CVE-2026-70494: Open WebUI: A folder write-collaborator can permanently delete the owner's chats by deleting a shared subfolder

The DELETE /api/v1/folders/{id} handler in backend/open_webui/routers/folders.py branched on whether the folder had a parent. Root folders required the owner or an admin. Subfolders accepted any write grant. Write grants flow down the folder tree, so a collaborator gained delete rights over every subfolder, including ones never explicitly shared with them.

The cascade that runs after the check is bound to the owner's id, not the caller's. Deleting a subfolder therefore removes the owner's chats and messages in that subtree for good. With delete_contents=false, the same request instead moved the owner's chats out of the folder without permission.

The attacker is a low-privilege account that the victim has already shared a folder with at write level. Nothing outside the shared subtree is reachable and no data is disclosed. The damage is integrity and availability: irreversible loss of another person's chat history, which matters when chats hold research, prompts or work product.

Open WebUI >= 0.10.0, < 0.11.0 with the Folders Sharing permission (user.permissions.sharing.folders) enabled. It is off by default. features.folders and chat.delete are on by default and are both required for the attack. Instances with sharing disabled and single-user instances are not affected. Check the version:

pip show open-webui

In the admin permissions settings, check whether folder sharing is enabled.

Upgrade to 0.11.0:

pip install --upgrade open-webui==0.11.0

Pull request 27003 replaces the root/subfolder split with one check: only the folder owner or an admin may delete, for root folders and subfolders alike. Collaborators can still create, rename and add to shared folders, and delete subfolders they own. No configuration change is needed. Until you upgrade, the advisory's preconditions imply turning off the folder sharing permission, though the sources do not list this as a workaround.

Look in application and proxy logs for DELETE /api/v1/folders/{id} calls made by users who do not own the folder, especially with delete_contents set. Owners may report chats that disappeared from a shared folder or moved out of it. Restore from backups of the Open WebUI database if you have them, since the deletion is permanent.

Summary

A user granted write access to a shared chat folder could permanently delete chats and messages belonging to the folder's owner. Deleting a folder cascades into the owner's chats and the entire subfolder subtree, and the deletion handler required only write access on subfolders instead of ownership. Root folders were restricted to the owner or an admin, subfolders were not.

Preconditions

The Folders Sharing permission (user.permissions.sharing.folders) must be enabled; it is off by default. The victim must have shared a folder with the attacker at write access. features.folders and the chat.delete permission are enabled by default and are both required. Deployments that leave folder sharing disabled are not affected, and neither are single-user instances.

Impact

Permanent, irreversible destruction of another user's chat history within and beneath a shared folder. With delete_contents=false the same request instead force-moved the owner's chats out of the folder, an unauthorized relocation rather than a deletion. The write grant on the shared root folder is inherited by every descendant, so the attacker could destroy subfolders that were never explicitly shared with them. Nothing outside the shared folder's subtree is reachable, and no data is disclosed that write access did not already expose.

Fix

Fixed in 0.11.0 by https://github.com/open-webui/open-webui/pull/27003. Folder deletion is now restricted to the folder owner or an admin for root folders and subfolders alike, replacing the previous root/subfolder split with a single check. Upgrading fully resolves the issue; no configuration change is required. Owners and admins are unaffected, and a write-collaborator can still create, rename and add to shared folders and delete subfolders they own.

Root cause

Affected component: backend/open_webui/routers/folders.py, the DELETE /api/v1/folders/{id} handler. Affected setup: any release from 0.10.0 onward that has folder sharing enabled.

The cascade that follows the authorization check is bound to the folder owner's id, not the caller's, so whoever passes the check deletes the owner's data. The check itself branched on whether the folder had a parent: root folders demanded ownership or admin, while subfolders accepted any write grant. Because write grants propagate down the folder tree, that branch handed every collaborator deletion rights over the owner's subtree, which is broader than what the sharing model grants write access.

Credits

@legobattman, who reported the issue and its remediation.