Executive brief
Open WebUI, a user interface for AI models, contains a flaw in its automation scheduling system that can be used to crash the service. By creating a specific type of recurring task, a user can force the system to perform excessive calculations that block all other users from accessing the interface. This results in a total service outage that persists even after the application is restarted until the problematic task is removed or the software is updated.
Technical details
The vulnerability exists in the `_parse_rule` function within `backend/open_webui/utils/automations.py`. When processing sub-daily recurrence rules (e.g., `FREQ=MINUTELY`), the parser uses a fixed anchor date of 2000-01-01 and synchronously iterates through every occurrence from that date to the present to determine the next run time. Because this occurs on the main asynchronous event loop, a single malicious rule can block the loop for tens of seconds. Furthermore, the scheduler re-evaluates these rules every 10 seconds, leading to a persistent denial-of-service state. The issue is fixed in version 0.11.0 by anchoring rules to the current time and bounding the number of allowed occurrences.
Affected products
- Open WebUI open-webui >= 0.9.0, < 0.11.0
Timeline
- 2026-08-02: patched: Fixed in version 0.11.0
- 2026-08-04: advisory: GitHub Advisory GHSA-73cq-mcgh-379c published