CVE-2026-87011 Open WebUI: Unauthenticated requests can stall the server via uncached OIDC fetches in back-channel logout
Unauthenticated attackers can cause denial of service in Open WebUI by sending invalid logout tokens that trigger uncached network fetches and block the event loop.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-87011?
CVE-2026-87011 is a high-severity denial of service vulnerability in Openwebui Open Webui, published on 9 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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/open_webui/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 ENABLE_OAUTH_BACKCHANNEL_LOGOUT was enabled. This issue is fixed in version 0.11.1.
Which versions are affected by CVE-2026-87011?
3 open source packages ship an affected version, including open-webui. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
open-webui PyPI | From 0.9.0 | 0.11.1 |
open-webui PyPI | From 0.9.0 | 0.11.1 |
open-webui PyPI | From 0.9.0 | 0.11.1 |
Products include Openwebui Open Webui.
How do I fix CVE-2026-87011?
Upgrade open-webui to 0.11.1 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-87011 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-87011 exists.
Other vulnerabilities in Openwebui Open Webui
- CVE-2026-44551 Open WebUI: LDAP Empty Password Authentication Bypass
- CVE-2026-56400 open-webui - Remote Code Execution via CORS Misconfiguration and Session Validation
- CVE-2024-8017 Cross-site Scripting (XSS) in open-webui/open-webui
- CVE-2026-45672 Open WebUI: Jupyter code execution works despite `ENABLE_CODE_EXECUTION=false` — feature gate bypassed
- CVE-2026-87995 Open WebUI: Same-origin XSS to account takeover via terminal port-preview iframe hardcoding allow-same-origin
Sources
Also known as GHSA-3g9q-v48f-hh9w, PYSEC-2026-4117.