Open WebUI: Any authenticated user can reach the Azure platform channel via server-side web fetch

Summary

Open WebUI fetches user-supplied URLs on the server for RAG URL ingestion and web search, and screens the resolved addresses so internal destinations cannot be reached. That screen decided whether a destination was external by asking Python's standard library whether the address is globally routable. Several addresses reserved for internal use answer yes to that question, including 168.63.129.16, the Azure platform channel every Azure virtual machine can reach. Any authenticated user could therefore make the server issue requests to those addresses and read the responses back through the API.

Preconditions

• The affected paths are the server-side URL fetches: RAG URL ingestion and web search. Both require an authenticated, verified account. No administrator role and no special workspace permission are needed.
• ENABLE_LOCAL_WEB_FETCH must be at its default of false. Setting it to true disables the address screen by design, and internal destinations are reachable on purpose.
• WEB_FETCH_FILTER_LIST is empty by default in affected versions, so no operator-supplied block entry covered these addresses unless one was added by hand.
• For the Azure platform channel specifically, the Open WebUI host must run on Azure (virtual machine, AKS, Container Apps or equivalent). That address is reachable from every Azure virtual machine regardless of network security group rules. On a host that is not on Azure the address routes nowhere and nothing is reachable through it.

Impact

An authenticated user could direct the server to issue GET requests at addresses reserved for internal use and receive the response body back in the API response, which also lands in the RAG context. On Azure that includes the platform channel, an endpoint the operator never intended to expose to application users. The same gap applied to the IPv4-translated range and to deprecated IPv6 site-local space, which on a host that routes them would reach internal services the same way.