CVE-2026-109299: Open WebUI 0.9.0 before 0.11.4 Denial of Service via Recurrence Rule Validation

Q: Who can exploit this issue?

An authenticated Open WebUI user who has automations permission can exploit it. The attack can be performed remotely through the automations create or update endpoints.

Q: What does an attacker need to submit?

The attacker submits an unsatisfiable recurrence rule, such as one specifying February 30th. Each such request can block the shared event loop for seconds, and repeated requests can stall the instance.

Q: Which deployments are affected?

Open WebUI versions from 0.9.0 up to, but not including, 0.11.4 are affected. The provided information does not state whether automations permission is granted by default.

Q: How can I determine whether my instance may be under attack?

Review requests to the automations create and update endpoints for unsatisfiable recurrence rules. Repeated invalid rules, particularly impossible dates, may correspond with periods where the shared event loop is blocked or the instance becomes stalled.

Published Oct 12, 2026

Updated

Open WebUI from 0.9.0 before 0.11.4 contains a denial of service vulnerability that allows authenticated users with automations permission to stall the instance by submitting unsatisfiable recurrence rules. Attackers can repeatedly send rules like February 30th to the automations create or update endpoints, blocking the shared event loop for seconds per request.

Affected Software

1 affected component

Open WebUI Open WebUI>=0.9.0<0.11.4

Remediation

Recommended actions to resolve this vulnerability, in priority order.

Upgrade
Upgrade Open WebUI to a version that resolves this vulnerability.
Fixed in 0.11.4

Event History

Oct 12, 2026

CVE Published

via MITRE·04:04 PM

Data Sourced

via MITRE·04:04 PM

DescriptionSeverityWeakness

Data Sourced

via NVD·05:17 PM

DescriptionSeverityWeakness

Frequently Asked Questions

Who can exploit this issue?

An authenticated Open WebUI user who has automations permission can exploit it. The attack can be performed remotely through the automations create or update endpoints.

What does an attacker need to submit?

The attacker submits an unsatisfiable recurrence rule, such as one specifying February 30th. Each such request can block the shared event loop for seconds, and repeated requests can stall the instance.

Which deployments are affected?

Open WebUI versions from 0.9.0 up to, but not including, 0.11.4 are affected. The provided information does not state whether automations permission is granted by default.

How can I determine whether my instance may be under attack?

Review requests to the automations create and update endpoints for unsatisfiable recurrence rules. Repeated invalid rules, particularly impossible dates, may correspond with periods where the shared event loop is blocked or the instance becomes stalled.

CVE-2026-109299: Open WebUI 0.9.0 before 0.11.4 Denial of Service via Recurrence Rule Validation

Affected Software

Remediation

Event History

Frequently Asked Questions

Who can exploit this issue?

What does an attacker need to submit?

Which deployments are affected?

How can I determine whether my instance may be under attack?

Company

Resources

Contact

Frequently Asked Questions

Who can exploit this issue?

What does an attacker need to submit?

Which deployments are affected?

How can I determine whether my instance may be under attack?