CVE-2026-88002: Open WebUI infinite loop denial of service in chat history reconstruction

CVE-2026-88002 · Severity: medium · CVSS 6.5 · Published 2026-09-09

Open WebUI is a web-based chat interface that allows users to create and store conversations. An authenticated user can craft a malicious chat with cyclic message references and omitted ID fields, causing the server's message-history reconstruction logic to enter an infinite loop. This blocks the entire server—all users lose access to the web interface, health checks fail, and orchestrator monitoring stops working—until an administrator manually deletes the malicious chat from the database or the server is restarted.

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

Quick answers

Is CVE-2026-88002 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-88002 being exploited in the wild.
How severe is CVE-2026-88002?
Medium severity, with a CVSS score of 6.5, published 9 September 2026.
Which products and versions are affected?
open-webui (PyPI) >= 0.5.0, < 0.11.1, ECOSYSTEM:introduced=0.5.0,fixed=0.11.1.
Is there a fix for CVE-2026-88002?
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-2026-88002 attacked?
It is attacked over the network, in a web application.
Am I affected by CVE-2026-88002?
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 a classic infinite-loop denial of service caused by a mismatch between loop traversal and visited-set tracking in `backend/open_webui/utils/misc.py`. The code walks a chat's message chain by following `parentId` keys in a history map, but tracks visited messages using their `id` field. When a message omits the `id` field (which the API does not validate), the visited guard fails to record it, allowing cycles to persist indefinitely. The walk is synchronous and runs on the asyncio event loop, so it blocks every concurrent request—including unauthenticated `/health` endpoints and administrator APIs. The malformed chat persists in the database across restarts, so the hang resumes on the next server restart. Any default-role user can trigger the attack via a single POST to create a chat followed by a GET to trigger history reconstruction. No authentication bypass, data exfiltration, or modification occurs. Fixed in version 0.11.1 by recording the traversal position (map key) instead of the message's self-reported `id` field, guaranteeing termination after at most one step per stored message.

Affected products

  • Open WebUI Open WebUI 0.5.0 to 0.11.0 inclusive

Identifiers

  • CVE-2026-88002
  • GHSA-jqhh-cjmq-vmv6
  • PYSEC-2026-3879

Timeline

  • 2026-08-29: disclosed
  • 2026-09-09: advisory: Published to GitHub Advisory Database
  • 2026: patched: Fixed in version 0.11.1 by commit 5c79ccc9e5c9efc2bc024d8f0b9757652ece929a

References

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