CVE-2026-87011: Open WebUI: Unauthenticated requests can stall the server via uncached OIDC fetches in back-channel logout
Open WebUI is an extensible, feature-rich, and user-friendly self-hosted AI platform. From 0.9.0 until 0.11.1, the unauthenticated POST /oauth/backchannel-logout handler in backend/openwebui/utils/oauth.py fetched the OIDC discovery document and signing keys before validating a submitted logout token. Each request repeated uncached network fetches, and the signing-key lookup blocked the async event loop, so requests carrying invalid tokens could stall the single-worker instance and amplify traffic to the identity provider when ENABLEOAUTHBACKCHANNELLOGOUT was enabled. This issue is fixed in version 0.11.1.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Open WebUIto a version that resolves this vulnerability.Fixed in 0.11.1
Event History
Frequently Asked Questions
Which deployments are exposed to this denial-of-service condition?
Open WebUI versions from 0.9.0 through 0.11.1 are affected when ENABLE_OAUTH_BACKCHANNEL_LOGOUT is enabled. The vulnerable endpoint is an unauthenticated POST handler, so no account or prior access is required.
What does an attacker need to do to trigger the impact?
An attacker can submit invalid logout tokens to POST /oauth/backchannel-logout. Before validating those tokens, the handler performs repeated uncached OIDC discovery and signing-key network fetches, with the signing-key lookup blocking the async event loop.
What is the likely operational impact?
On a single-worker instance, invalid-token requests can stall the server and cause a denial of service. They can also amplify request traffic to the configured identity provider.
What can be done if upgrading is not immediately possible?
Disable ENABLE_OAUTH_BACKCHANNEL_LOGOUT to remove the affected handler behavior. Upgrade to version 0.11.1 when possible.