The vulnerability in Open WebUI allows authenticated users with low privileges to query the list of active background tasks and stop tasks belonging to other users via the GET /api/tasks and POST /api/tasks/stop/{task_id} endpoints. This flaw leads to intentional cancellation of other users’ long‑running tasks, which can be used to shut down system‑wide chat functionality for the entire deployment. The primary impact is a denial of service that harms availability and disrupts the user experience.

The affected product is the Open WebUI self‑hosted AI platform prior to version 0.9.0. Users running any earlier release of the platform are potentially impacted; the fix is included in 0.9.0 and later releases.

The CVSS score of 7.1 indicates a high severity vulnerability. Since the EPSS score is not available, the precise likelihood of exploitation is unknown, but the vulnerability is considered high risk because any authenticated low‑privileged user can abuse it. No exploit code is publicly known and it is not listed in the CISA KEV catalog, yet the ease of access through a normal user account means that systems without the upgrade are at significant risk of service disruption.