CVE-2026-57571 affects crawl4ai versions before 0.9.0. The vulnerability arises because the crawler uses attacker-influenced input for the destination filename without restricting the path to the downloads directory. Specifically, the HTTP crawler uses the Content-Disposition filename from responses, and the browser crawler uses the suggested download filename. This lack of confinement allows path traversal attacks, enabling arbitrary file writes with attacker-controlled content. Such writes can escalate to remote code execution. The vulnerability is resolved in version 0.9.0.

An attacker can write arbitrary files to the filesystem outside the intended downloads directory, potentially leading to remote code execution. The CVSS v3.1 score is 9.6 (critical), reflecting network attack vector, low attack complexity, no privileges required, user interaction required, scope change, and high confidentiality, integrity, and availability impacts.

Upgrade crawl4ai to version 0.9.0 or later, where this path traversal vulnerability is fixed. No other mitigation or temporary workaround is indicated. Patch status is confirmed fixed in 0.9.0.