Crawl4AI: Multiple Docker API Vulnerabilities - File Write, SSRF, Auth Bypass, XSS, JS Execution

Summary

Multiple security vulnerabilities in the Crawl4AI Docker API server affecting endpoints for crawling, markdown/LLM extraction, screenshots, PDFs, webhooks, monitoring, JavaScript execution, and configuration.

Vulnerabilities

1. Arbitrary File Write via /screenshot and /pdf (CWE-22, CVSS 9.1)

The output_path parameter accepts arbitrary filesystem paths with no validation. An attacker can overwrite server files (DoS) or write to any appuser-writable location.

Fix: Added validate_output_path() restricting writes to CRAWL4AI_OUTPUT_DIR (/tmp/crawl4ai-outputs by default). Added Pydantic field_validator rejecting .. traversal sequences.

2. SSRF via Webhook URL (CWE-918, CVSS 8.6)

Webhook URLs in /crawl/job and /llm/job accept internal/private IPs with no validation, enabling Server-Side Request Forgery against cloud metadata endpoints (169.254.169.254), internal services, and Docker networks.

Fix: Added validate_webhook_url() with blocklist for RFC 1918, loopback, link-local, cloud metadata IPs and hostnames. Validation at both job submission and send time. Explicit follow_redirects=False.

3. Authentication Bypass on Monitor Endpoints (CWE-306, CVSS 6.5)

The monitor router was mounted without token_dep dependency, making all monitoring endpoints (including destructive ones like /monitor/actions/cleanup) accessible without authentication.

Fix: Added dependencies=[Depends(token_dep)] to monitor router. Added explicit token check on WebSocket /monitor/ws endpoint.

4. Stored XSS in Monitor Dashboard (CWE-79, CVSS 6.1)

URLs and error messages rendered in the monitor dashboard via innerHTML without escaping, enabling stored XSS via crafted crawl URLs.

Fix: Server-side html.escape() on URL and error storage. Client-side escapeHtml() wrapper on all innerHTML template injections.

5. Arbitrary JavaScript Execution via /execute_js (CWE-94, CVSS 8.1)

The /execute_js endpoint accepts and executes arbitrary JavaScript in the server's browser with --disable-web-security enabled, combining arbitrary JS execution with SSRF capability.

Fix: Disabled by default via CRAWL4AI_EXECUTE_JS_ENABLED env var. Added SSRF blocklist on destination URL. Removed --disable-web-security from default browser args.

6. Hardcoded JWT Secret Key (CWE-798, CVSS 9.8)

The JWT signing key defaults to "mysecret" in the public source code, allowing anyone to forge valid authentication tokens.

Fix: Removed default value. Added startup validation rejecting weak/short secrets. Auto-generates ephemeral key when JWT enabled but no key set.

7. SSRF via Direct Crawl Endpoints /crawl, /md, /llm (CWE-918, CVSS 8.6)

The primary crawl entry points (/crawl, /crawl/stream, /md, /llm) fetch arbitrary user-supplied URLs with no destination validation, enabling Server-Side Request Forgery against internal services, Docker networks, and cloud metadata endpoints (169.254.169.254). A blocklist that only inspects the literal hostname is additionally bypassable via IPv6-mapped IPv4 addresses (e.g. [::ffff:169.254.169.254], [::ffff:10.0.0.1]), which resolve to the blocked private/metadata ranges but evade a naive string check.

Fix: Added URL destination validation on all crawl/md/llm entry points, reusing the SSRF blocklist (RFC 1918, loopback, link-local, cloud-metadata IPs and hostnames). IPv6-mapped IPv4 addresses are normalized to their IPv4 form before the blocklist check, closing the mapping bypass. raw:// URLs are skipped. Validation applies at request entry, not only at fetch time.

Workarounds

1. Upgrade to the patched version (recommended)
2. Set CRAWL4AI_API_TOKEN to enable authentication
3. Set a strong SECRET_KEY (min 32 chars) if using JWT
4. Restrict network access to the Docker API

Credits

• Jeongbean Jeon - file write, SSRF, monitor auth bypass, stored XSS
• wulonchia - file write via output_path (independent report)
• by111 (August829) - hardcoded JWT, eval in /config/dump, /execute_js, hook sandbox escape
• secsys_codex - SSRF via /md, /crawl, /llm endpoints + IPv6-mapped IPv4 bypass (URL destination validation)
• Velayutham Selvaraj (LinkedIn) - SSRF via missing host validation in validate_url_scheme (independent report)
• IcySun & Yashon - SSRF, arbitrary file write, missing-auth-by-default, hook sandbox bypass via asyncio (independent report)