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

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). 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
    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

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