Open WebUI: Unauthenticated endpoint can trigger embedding generation (cost/DoS)

Summary

GET /api/v1/memories/ef is accessible without authentication and executes request.app.state.EMBEDDING_FUNCTION(...). This allows any unauthenticated caller to trigger embedding generation which can lead to direct cost exposure if a paid provider is used. Code reference: backend/open_webui/routers/memories.py (@router.get("/ef") -> calls request.app.state.EMBEDDING_FUNCTION("hello world")).

Details

GET /api/v1/memories/ef is reachable without authentication and triggers request.app.state.EMBEDDING_FUNCTION("hello world"). This crosses an intended security boundary by allowing unauthenticated users to invoke potentially expensive embedding computation and/or paid upstream embedding APIs.

PoC

1. Start Open WebUI in default configuration (no special env hardening; default ENABLE_MEMORIES is true).
2. From an unauthenticated client (no cookies/Authorization header), call: curl -i http://<host>:<port>/api/v1/memories/ef 3. Observe the server performs embedding generation and returns a response like:
   • HTTP 200 with JSON containing the result.

How it can be abused / attacker actions:

• Send repeated requests to /api/v1/memories/ef to:
  • consume CPU/GPU resources (DoS)
  • generate sustained outbound usage to embedding providers if configured (cost + rate-limit exhaustion)
  • degrade latency/availability for legitimate users

Impact

If embeddings are configured to use paid/remote providers (OpenAI/Azure/etc), an attacker can generate unlimited requests and incur charges.

Resolution

Fixed in commit e5035ea31, first released in v0.8.0 (Feb 2026). The /api/v1/memories/ef route was removed entirely. It was a diagnostic/debug-style endpoint that hard-coded "hello world" through the embedding function without any authentication dependency; there was no legitimate caller that depended on it, so deletion was the cleaner fix than retrofitting auth. Users on >= 0.8.0 are not affected.