CVE-2026-91943 in Crawl4AI
Summary
by MITRE • 09/15/2026
Crawl4AI before 0.9.3 contains a server-side request forgery vulnerability in PDFContentScrapingStrategy where _get_pdf_path() re-downloads targets with Python requests without egress validation. Authenticated attackers can supply URLs that redirect to internal addresses or use DNS rebinding to access internal services, exfiltrating responses through PDF text extraction in crawl results.
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Analysis
by VulDB Data Team • 09/15/2026
The vulnerability identified in Crawl4AI versions prior to 0.9.3 represents a critical server-side request forgery flaw within the PDFContentScrapingStrategy component. This issue stems from the _get_pdf_path() function, which is responsible for retrieving and processing PDF documents during web crawling operations. The core technical deficiency lies in the absence of egress validation when utilizing Python's requests library to download target resources. By failing to restrict or verify the destination URLs before initiating network connections, the application allows attackers to manipulate the request flow toward internal infrastructure that should remain inaccessible from external contexts.
Authenticated users can exploit this flaw by supplying maliciously crafted URLs as targets for crawling operations. These URLs are designed to redirect to private IP addresses or utilize DNS rebinding techniques to resolve to local hostnames such as localhost or 127.0.0.1. Once the server processes these requests, it acts as a proxy, fetching content from internal services like administrative panels, database interfaces, or other backend APIs that are not exposed to the public internet. This effectively bypasses network-level access controls and firewalls that rely on source IP verification, allowing the attacker to interact with internal systems through the vulnerable application's outbound traffic capabilities.
The operational impact of this vulnerability is severe due to the mechanism by which exfiltrated data is returned to the attacker. The extracted content from the targeted PDFs or redirected responses is integrated into the crawl results and subsequently made available for text extraction. This means that sensitive information retrieved from internal services, such as configuration files, user credentials, database dumps, or proprietary business logic, can be read directly by the authenticated attacker through the application's output channels. The ability to exfiltrate data in this manner transforms a simple SSRF into a potent tool for comprehensive internal network reconnaissance and data theft.
From a classification perspective, this vulnerability aligns with CWE-918 Server-Side Request Forgery (SSRF), specifically involving improper validation of user-supplied URLs before making server-side requests. It also relates to CWE-20 Improper Input Validation regarding the lack of egress filtering rules. In terms of attack tactics, this exploitation method corresponds to ATT&CK technique T1598 Phishing for Information within a Network or more accurately T1499 Endpoint Denial of Service if used disruptively, but primarily it fits under T1071 Application Layer Protocol for communication and T1046 Network Service Discovery when scanning internal services. The use of DNS rebinding further connects to techniques involving domain fronting or evasion of network security controls by manipulating name resolution processes.
To mitigate this vulnerability, immediate updates to Crawl4AI version 0.9.3 or later are required as the issue has been addressed in subsequent releases. For environments where upgrading is not immediately feasible, implementing strict egress filtering at the network level can help restrict outbound connections from the application server to only known and necessary destinations. Additionally, applying input validation on URL parameters passed to crawling functions ensures that only whitelisted domains or IP ranges are permitted for processing. Enforcing DNS resolution checks within the application code before initiating requests can also prevent redirection attacks by validating that resolved IPs do not fall into private address spaces defined in RFC 1918.