CVE-2026-51031 in FlareSolverr
Summary
by MITRE • 07/21/2026
FlareSolverr before version 3.4.7 contains a server-side request forgery (SSRF) vulnerability in the /v1 API endpoint. This allows a remote attacker to obtain sensitive information
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Analysis
by VulDB Data Team • 07/21/2026
The FlareSolverr vulnerability represents a critical server-side request forgery flaw that undermines the security posture of this web-based automation tool designed for handling JavaScript-heavy websites. This vulnerability specifically affects versions prior to 3.4.7 and manifests within the /v1 API endpoint, making it accessible to remote attackers without authentication requirements. The flaw enables malicious actors to manipulate the application's request handling mechanisms to access internal resources that should remain isolated from external networks.
The technical implementation of this SSRF vulnerability stems from insufficient input validation and sanitization within the API endpoint processing logic. When FlareSolverr receives requests through the /v1 endpoint, it fails to properly validate user-supplied parameters that control the target URL for scraping operations. Attackers can exploit this by crafting malicious requests that include specially formatted URLs or IP addresses pointing to internal systems or services. The application processes these requests without adequate restrictions, allowing it to make HTTP requests to arbitrary destinations including internal network resources, localhost, or other systems within the same network segment.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can enable attackers to perform reconnaissance activities against internal infrastructure. Remote threat actors could leverage this flaw to discover running services on internal networks, potentially identifying vulnerable systems, databases, or administrative interfaces that would otherwise remain hidden from external view. The vulnerability's exploitation capability allows for cascading attacks where initial reconnaissance leads to further compromise of the underlying network environment, particularly in scenarios where FlareSolverr operates within trusted network boundaries.
Security professionals should recognize this vulnerability as a direct implementation of CWE-918 Server-Side Request Forgery, which specifically addresses the risk of applications making unintended requests to internal resources. The attack pattern aligns with ATT&CK technique T1071.004 Application Layer Protocol Web Protocols where adversaries leverage web application vulnerabilities to access internal systems. Organizations running FlareSolverr should implement immediate mitigations including upgrading to version 3.4.7 or later, implementing network segmentation controls, and configuring proper input validation at the API gateway level. Additional protective measures include restricting access to the /v1 endpoint through firewall rules, implementing strict URL validation policies, and deploying web application firewalls to monitor and block suspicious request patterns that could indicate exploitation attempts.