Open WebUI from 0.11.0 before 0.11.4 contains an improper authorization vulnerability in the chat fork handler, which places forked chats in the… (CVE-2026-109284)

The vulnerability in Open WebUI (versions >=0.11.0 <0.11.4) involves improper authorization in the chat fork handler. Specifically, when a user forks a chat via the POST /api/v1/chats/{id}/fork endpoint, the system places the forked chat in the source chat's folder without checking if the user currently has write access to that folder. Consequently, users who were previously granted write access but have since been downgraded to read-only can still fork chats they created during their write access period, inserting chats controlled by them into folders accessible by other members. This violates access control policies and can lead to unauthorized content visibility.

The vulnerability allows users with downgraded permissions to insert unauthorized chats into shared folders, potentially exposing folder owners and members to attacker-controlled content. The impact is limited to integrity (insertion of unauthorized chats) without direct confidentiality or availability impact. The CVSS score of 4.3 (medium severity) reflects this limited impact and the requirement for some privileges (low privileges) to exploit.

A fixed version is available starting from Open WebUI version 0.11.4 that addresses this improper authorization issue. Users should upgrade to version 0.11.4 or later to remediate this vulnerability. Since no vendor advisory or patch links were provided, verify the patch status with the official Open WebUI release notes or vendor advisory before deployment.