CVE-2026-109238 in Crawl4AI
Summary
by MITRE • 10/12/2026
Crawl4AI 0.7.0 before 0.9.4 contains a server-side request forgery vulnerability that allows API clients to reach internal addresses by enabling link_preview_config on /crawl requests. Attackers can supply a controlled page with include_external and include_patterns set, causing AsyncUrlSeeder to fetch internal, private, and cloud-metadata links and return their parsed head data.
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Analysis
by VulDB Data Team • 10/12/2026
Crawl4AI versions prior to 0.9.4 are susceptible to a Server-Side Request Forgery vulnerability within the /crawl endpoint when specific configuration parameters are manipulated by an API client. This flaw arises from the improper validation of user-supplied input in the link_preview_config parameter, which dictates how external links and patterns are processed during web crawling operations. By enabling this configuration option, attackers can instruct the underlying AsyncUrlSeeder component to fetch resources that were not intended for public access. The vulnerability specifically exploits the ability to set include_external and include_patterns flags, allowing the application to traverse beyond its designated scope and reach internal network addresses, private IP ranges, and cloud metadata endpoints.
The technical mechanism of this exploitation involves an attacker submitting a controlled page or URL as part of the crawl request while simultaneously configuring the link_preview_config to permit external links and specific pattern matching. Once these conditions are met, the AsyncUrlSeeder component initiates HTTP requests from the server itself rather than just returning static data about the initial target. This server-side execution allows the attacker to probe internal infrastructure that is typically isolated from direct internet access. The application returns parsed head data for these fetched resources, effectively leaking sensitive information such as headers, status codes, and potentially content snippets from internal services or cloud provider metadata endpoints like AWS EC2 instance metadata service 169.254.169.254 or Azure managed identity endpoints.
From an operational perspective, this vulnerability poses a significant risk to organizations relying on Crawl4AI for web scraping or data aggregation tasks. The ability to access internal addresses can lead to unauthorized discovery of backend services, database ports, and administrative interfaces that are not exposed to the public internet. Furthermore, accessing cloud metadata endpoints may result in the exfiltration of temporary security credentials, IAM roles, and other sensitive configuration details stored by the underlying infrastructure provider. This information is often critical for subsequent stages of an attack chain, including privilege escalation or lateral movement within a compromised environment. The vulnerability aligns with CWE-918 Server-Side Request Forgery due to insufficient validation of user-controlled input that influences server-side network requests. It also maps to MITRE ATT&CK technique T1560.002 Data Staged via Cloud Infrastructure, as attackers can use the fetched metadata and internal responses to stage data for exfiltration or further reconnaissance within cloud environments.
To mitigate this vulnerability, organizations should immediately upgrade Crawl4AI to version 0.9.4 or later where these input validation checks have been strengthened. In cases where upgrading is not immediately feasible, administrators can implement network-level controls such as firewall rules or reverse proxy configurations to block outbound requests from the application server to private IP ranges and cloud metadata endpoints. Additionally, applying strict allowlists for permitted external domains in the link_preview_config parameter can prevent unauthorized traversal of internal networks. It is also recommended to disable unnecessary features like include_external if they are not required for specific use cases, thereby reducing the attack surface available to potential adversaries exploiting this flaw.