CVE-2026-88000: Open WebUI denial of service via cyclic chat tree message deletion

CVE-2026-88000 · Severity: medium · CVSS 6.5 · Published 2026-09-09

Open WebUI is a user-friendly AI chat interface that stores conversation histories as JSON. A flaw in the message deletion logic allows any authenticated user to craft a chat with messages that reference each other as children (a cycle), then delete a message to trigger an infinite loop. This loop blocks all requests from all users—including admin endpoints and health checks—effectively taking down the entire service until the affected worker process is manually killed.

Technologies: open-webui (PyPI). Vendors: PyPI.

Quick answers

Is CVE-2026-88000 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-88000 being exploited in the wild.
How severe is CVE-2026-88000?
Medium severity, with a CVSS score of 6.5, published 9 September 2026.
Which products and versions are affected?
open-webui (PyPI) >= 0.10.0, < 0.11.1, ECOSYSTEM:introduced=0.10.0,fixed=0.11.1.
Is there a fix for CVE-2026-88000?
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-2026-88000 attacked?
It is attacked over the network, in a web application.
Am I affected by CVE-2026-88000?
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 is an infinite loop (CWE-835) in the chat history message deletion handler at `backend/open_webui/models/chats.py`, reachable via `DELETE /api/v1/chats/{id}/messages/{message_id}`. The root cause is that when resolving a message's new current pointer after deletion, the code walks the `childrenIds` tree without maintaining a visited set, and does not validate chat structure when created. An attacker with default user role creates a malformed chat (≈300 bytes) where two messages reference each other as children, then issues a single delete request. The synchronous walk runs on the asyncio event loop, pinning one CPU core indefinitely and blocking every other user's request until the worker is killed. The attack is fire-and-forget; disconnection does not cancel the work. Fixed in version 0.11.1 by recording visited node IDs, ensuring termination in O(n) steps regardless of message structure.

Affected products

  • Open WebUI open-webui 0.10.0 to 0.11.0 (inclusive)

Identifiers

  • CVE-2026-88000
  • GHSA-3cgp-3cqx-j8w2
  • PYSEC-2026-3877

Timeline

  • 2026-09-09: disclosed: GHSA published
  • 2026-09-09: patched: Fix released in version 0.11.1 via commit b933292

References

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