Executive brief
Crawl4AI is an open-source tool used to crawl and scrape websites for use with Large Language Models (LLMs). A security flaw in its Docker API server allows unauthorized users to bypass security filters and force the server to connect to internal network resources or cloud metadata services. This could lead to the exposure of sensitive internal data or cloud service credentials, potentially compromising the entire hosting environment.
Technical details
A Server-Side Request Forgery (SSRF) vulnerability exists in Crawl4AI's Docker API server due to insufficient validation in the 'validate_webhook_url' and 'validate_url_destination' functions. The protection mechanism relied on an explicit CIDR blocklist that failed to account for various IPv6 transition forms (such as NAT64, 6to4, and IPv4-mapped addresses) and the IPv6 unspecified address. An unauthenticated remote attacker can exploit this by submitting specially crafted URLs to API endpoints (e.g., /crawl, /md, /crawl/job), causing the server to bypass filters and access internal-only services or cloud metadata endpoints (like 169.254.169.254). The issue is fixed in version 0.8.8 by implementing a more robust check that rejects any non-global IP addresses.
Affected products
- unclecode crawl4ai < 0.8.8
Timeline
- 2026-06-04: advisory: GitHub advisory published by maintainers
- 2026-06-23: disclosed: CVE published to NVD