CVE-2026-88001

## Summary Open WebUI protects server-side web fetches with two controls: the operator's list of excluded hosts, and a check that refuses private and internal addresses. Neither control was applied to the destination of an HTTP redirect. On a deployment where redirect following is enabled, any authenticated user who can cause the server to fetch a URL could submit a page that redirects, and the server would fetch the redirect destination without either control being applied to it. The server therefore connects to hosts the operator excluded, and to internal addresses including loopback, private networks and cloud metadata endpoints. ## Preconditions `AIOHTTP_CLIENT_ALLOW_REDIRECTS` must be set to `true`. Its default is `false`, and on the default the affected fetch paths do not follow redirects at all, so a deployment that has not changed this setting is not affected. The attacker needs an authenticated account of any role, with access to any feature that causes the server to fetch a URL. Web search, ingesting a URL into a collection, the built-in page fetch tool and image URLs in chat all reach it. No internal hostnames need to be known, because the loopback and cloud metadata addresses are fixed and identical on every deployment. Neither `ENABLE_LOCAL_WEB_FETCH` at its default of `false` nor any set of entries in `WEB_FETCH_FILTER_LIST` prevents this. ## Impact An authenticated user can make the server issue requests to hosts the operator deliberately excluded, and to addresses on the internal network including loopback, private ranges and the cloud metadata endpoints of the major providers. What reaches the attacker depends on which HTTP client the fetch path uses, and is stated here as verified rather than assumed. On the paths built on `requests`, the fetched body is returned to the caller, so the response of an excluded host is readable: the built-in page fetch tool hands it to the model, and the URL ingestion endpoint returns it in its response. Those