Crawl4AI: Unauthenticated SSRF on the Docker server streaming crawl path (/crawl/stream)

Overview

Summary

The Docker API server applied its SSRF destination check (validate_url_destination) on the non-streaming /crawl path but not on the streaming path. handle_stream_crawl_request passed seed URLs straight to the crawler with no destination validation. A remote, unauthenticated client could call POST /crawl/stream (or POST /crawl with crawler_config.stream=true, which short-circuits to the same handler) with a URL pointing at an internal, private, or link-local address; the server fetched it and streamed the response body back. The Docker API is unauthenticated by default.

Affected paths

POST /crawl/stream, and POST /crawl with crawler_config.stream=true (both route to handle_stream_crawl_request, deploy/docker/api.py).

Impact

Unauthenticated read server-side request forgery: an attacker reads internal-only services and cloud-metadata endpoints (e.g. http://169.254.169.254/ for IAM credentials), with the response body streamed back. This is the same class and severity as the project's prior "SSRF via Direct Crawl Endpoints" advisory; /crawl/stream is part of that endpoint family and was never covered by the destination check.

Fix

handle_stream_crawl_request now validates every seed URL's destination with the same global-routability check as handle_crawl_request, before any fetch. The SSRF regression test was hardened to assert per-handler coverage (including the streaming handler) rather than a bare occurrence count, which previously let this gap pass.

Workarounds

• Upgrade to the patched version (0.9.0).
• Enable authentication and restrict who can reach the API (note: this does not constrain which URL the API fetches).
• Restrict the container's outbound network access (egress firewall / no metadata route).

Credits

KOH Jun Sheng - reported the streaming-path SSRF with a runnable PoC and noted the count-based regression test that masked it, plus the shared root cause with redirect/deep-crawl link following.

Affected packages

• crawl4ai < 0.9.0

Remediation

Upgrade to a patched release:

• crawl4ai 0.9.0