# CVE-2026-87011: Open WebUI OIDC back-channel logout denial of service

Source: https://junglewise.ai/threats/cve-2026-87011-open-webui-oidc-back-channel-logout-denial-of-service  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-09. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-87011 · Severity: high · CVSS 7.5 · Published 2026-09-09

Open WebUI's identity provider logout handler can be forced to repeatedly fetch and re-validate encryption keys from the OIDC provider without caching, causing the application's single worker process to become unresponsive. An attacker with network access can send a small number of forged logout requests to stall the entire service for several seconds, blocking all chat and API requests until the server recovers.

Technologies: [open-webui (PyPI)](https://junglewise.ai/threats/technologies/open-webui). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2026-87011 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-87011 being exploited in the wild.

**How severe is CVE-2026-87011?** High severity, with a CVSS score of 7.5, published 9 September 2026.

**Which products and versions are affected?** open-webui (PyPI) >= 0.9.0, <= 0.11.0, ECOSYSTEM:introduced=0.9.0,fixed=0.11.1.

**Is there a fix for CVE-2026-87011?** Yes. open-webui (PyPI): upgrade to 0.11.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-87011 attacked?** It is attacked over the network, in a web application.

**Am I affected by CVE-2026-87011?** Check whether you run open-webui (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- open-webui (PyPI): upgrade to 0.11.1 or later

  ```sh
  pip install "open-webui>=0.11.1"
  ```


## Technical details

The vulnerability exists in the OIDC back-channel logout handler (`backend/open_webui/utils/oauth.py`, endpoint `POST /oauth/backchannel-logout`). The handler is intentionally unauthenticated because identity providers call it without a browser session. However, before validating the logout token's signature, the code opens a new HTTP session per request to fetch the provider's discovery document and signing keys (JWKS), with no caching between requests. The JWKS client fetch runs as a blocking (synchronous) call directly on the async event loop. An attacker can send requests with invalid tokens (e.g., four-character signatures) to trigger these expensive operations repeatedly. On version 0.11.0, 60 concurrent requests caused an 8.3-second event-loop stall, during which no other requests are answered. The fix (version 0.11.1) caches both the discovery document and signing keys per provider, makes fetches asynchronous, and rejects tokens lacking a `kid` header before any network lookups. Preconditions: `ENABLE_OAUTH_BACKCHANNEL_LOGOUT=true` (not default but recommended in hardening docs) and at least one OIDC provider configured.

## Affected products

- Open WebUI Open WebUI 0.9.0 through 0.11.0

## Identifiers

- CVE-2026-87011
- GHSA-3g9q-v48f-hh9w
- PYSEC-2026-4117

## Timeline

- 2026-09-04: disclosed
- 2026-09-10: advisory
- 2026-09-10: patched: Version 0.11.1 released

## References

- [https://api.github.com/users/galanko](https://api.github.com/users/galanko)
- [https://github.com/galanko](https://github.com/galanko)
- [https://api.github.com/users/galanko/gists%7B/gist_id%7D](https://api.github.com/users/galanko/gists%7B/gist_id%7D)
- [https://api.github.com/users/galanko/repos](https://api.github.com/users/galanko/repos)
- [https://avatars.githubusercontent.com/u/21973853?v=4](https://avatars.githubusercontent.com/u/21973853?v=4)
- [https://api.github.com/users/galanko/events%7B/privacy%7D](https://api.github.com/users/galanko/events%7B/privacy%7D)

## Related threats

- [Open WebUI OAuth token exchange authorization bypass](https://junglewise.ai/threats/cve-2026-88006-open-webui-oauth-token-exchange-authorization-bypass)
- [Open WebUI OAuth token exchange authorization bypass](https://junglewise.ai/threats/cve-2026-88005-open-webui-oauth-token-exchange-authorization-bypass)
- [Open WebUI infinite loop denial of service in chat history reconstruction](https://junglewise.ai/threats/cve-2026-88002-open-webui-infinite-loop-denial-of-service-in-chat-history)
- [Open WebUI server-side request forgery via unvalidated HTTP redirects](https://junglewise.ai/threats/cve-2026-88001-open-webui-server-side-request-forgery-via-unvalidated-http)
- [Open WebUI denial of service via cyclic chat tree message deletion](https://junglewise.ai/threats/cve-2026-88000-open-webui-denial-of-service-via-cyclic-chat-tree-message)