CVE-2026-87998: Open WebUI: Non-admin users can delete admin-owned external knowledge connections via knowledge base deletion

Summary External knowledge connections are created and owned by administrators, and are shared by every external knowledge base bound to them. Deleting an external knowledge base also removed that connection from the instance configuration, with no check on the caller's role and no check for other knowledge bases still using it. Any authenticated user holding a write grant on a single external knowledge base could therefore wipe a shared connection that other knowledge bases depend on, and the dedicated administrator route for deleting a connection explicitly refuses that same operation while the connection is still in use.

Preconditions The deployment uses external knowledge bases, backed by the qdrant, milvus or pgvector external providers. Instances with only local knowledge bases are not affected.

An administrator created at least one external connection and at least one external knowledge base bound to it. Both of those actions are admin-only.

The attacker is an ordinary authenticated user holding a write grant on one of those external knowledge bases. A read grant is not enough, and an unrelated user cannot reach the route at all.

The damage scales with sharing. It is worst when one connection backs several knowledge bases, because deleting a single knowledge base destroys the connection for all of them.

Impact An ordinary user removes instance-wide configuration that only administrators can create or manage. Every other external knowledge base bound to the deleted connection keeps its stored connection id and stops working: retrieval against it fails with "External knowledge connection not found", so those knowledge bases return nothing in chat until an administrator recreates the connection by hand. The stored credential goes with it, and connection API responses strip credentials, so an administrator who did not keep the key elsewhere cannot restore the connection without obtaining it again.

Nothing is disclosed to the attacker and the external vector store itself is untouched. What is lost is Open WebUI's own connection configuration, and the availability of the knowledge bases that depend on it.

Fix Fixed in 0.11.1 by https://github.com/open-webui/open-webui/pull/28113. Deleting an external knowledge base now clears its connection only when the caller is an administrator and the knowledge base being deleted is the last one referencing that connection, matching the dedicated connection delete route. Upgrading resolves the issue with no configuration change required.

Root cause Affected component: the knowledge base delete handler in backend/openwebui/routers/knowledge.py, reached through DELETE /api/v1/knowledge/{id}/delete.

Affected setup: every release from 0.10.0, where external knowledge connections were introduced, up to and including 0.11.0.

The handler authorized the caller against the knowledge base, which a write grant satisfies, and then performed a second, unrelated operation against global configuration in the same request. That second step carried no authorization of its own. It neither required the administrator role that creating a connection requires, nor counted the other knowledge bases still bound to the connection. The dedicated route DELETE /api/v1/knowledge/external/connections/{id} already performed both checks, so an outcome an administrator was blocked from was reachable by a non-administrator through the knowledge base route.

Proof of concept Reproduced against a local instance on 0.11.0 with default settings, and against 0.11.1 for comparison.

An administrator created one external connection and two external knowledge bases bound to it, then granted a plain user write access on the first knowledge base. As that user:

DELETE /api/v1/knowledge/{KBA}/delete Authorization: Bearer <user token>

On 0.11.0 the request returns 200 true. The administrator connection list then returns zero connections, the second knowledge base still carries the deleted connection id, and retrieving from it raises "External knowledge connection not found".

On 0.11.1 the same request deletes the knowledge base, the connection list still returns the connection, and the second knowledge base is unaffected. An administrator deleting the last remaining knowledge base on that connection still clears it, so the intended cleanup is preserved.

Credits @Bellingham-max, for reporting the missing authorization on the shared connection teardown.