CVE-2026-57573 in Crawl4AI
Summary
by MITRE • 07/07/2026
Crawl4AI is an open-source LLM-friendly web crawler and scraper. Prior to 0.9.0, the Docker API server applied its SSRF destination check 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, allowing a remote unauthenticated client to call POST /crawl/stream or POST /crawl with crawler_config.stream=true with a URL pointing at an internal, private, or link-local address; the server fetched it and streamed the response body back. This issue is fixed in version 0.9.0.
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Analysis
by VulDB Data Team • 07/07/2026
The vulnerability in Crawl4AI represents a critical server-side request forgery flaw that exploited inconsistent security controls across different API endpoints within the Docker API server. This weakness allowed remote unauthenticated attackers to bypass destination validation mechanisms that were properly implemented on non-streaming paths but omitted from streaming paths, creating a significant attack surface that could be leveraged for internal network reconnaissance and data exfiltration. The issue specifically affected versions prior to 0.9.0 where the handle_stream_crawl_request function failed to validate destination URLs before initiating requests to internal or private addresses, enabling attackers to target sensitive internal resources through the streaming API endpoints.
The technical implementation of this vulnerability stems from a design inconsistency in the crawler's security validation logic where the streaming endpoint /crawl/stream did not perform the same destination checks that were applied to the standard /crawl path. When clients made POST requests to either endpoint with crawler_config.stream=true, the system would process seed URLs without validating whether they pointed to internal network addresses such as private IP ranges, loopback interfaces, or link-local addresses. This validation gap allowed attackers to craft malicious requests that would cause the server to make HTTP requests to internal services, potentially exposing sensitive information from internal systems that should not be accessible from external networks.
The operational impact of this vulnerability extends beyond simple information disclosure, as it enabled attackers to perform internal network reconnaissance by targeting various internal services and resources. The streaming nature of the vulnerability meant that attackers could not only access internal content but also receive responses in real-time through the streaming interface, making it particularly dangerous for exfiltrating large amounts of data or conducting continuous monitoring of internal systems. This capability aligns with attack techniques described in the MITRE ATT&CK framework under initial access and reconnaissance phases, where adversaries seek to map internal network topology and identify valuable targets within private networks.
The security implications of this flaw are particularly severe given that Crawl4AI is designed as an LLM-friendly web crawler and scraper that might be deployed in environments where it could have access to sensitive internal resources. The vulnerability essentially allowed attackers to use the legitimate crawling functionality as a vector for unauthorized network access, potentially compromising internal systems that were not intended to be directly accessible from external networks. This represents a classic example of improper input validation and insufficient access controls, which are commonly categorized under CWE-918 Server-Side Request Forgery. The fix implemented in version 0.9.0 involved ensuring consistent destination validation across all API endpoints, requiring that both streaming and non-streaming paths perform the same security checks before processing any seed URLs.
Organizations deploying Crawl4AI should implement immediate mitigations including updating to version 0.9.0 or later, reviewing network access controls for the Docker API server, and implementing additional monitoring for unusual outbound connections from the crawling service. The vulnerability demonstrates the importance of consistent security implementations across all API endpoints and highlights the need for comprehensive input validation regardless of request type or streaming behavior. Security teams should also consider implementing network segmentation to limit the potential impact of such vulnerabilities and establish proper access controls for internal services that might be targeted through legitimate crawling functionality.