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CVE-2026-56258 – Arbitrary File Write Leading to RCE – Crawl4AI before 0.8.8

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Summary

CVE-2026-56258 is an arbitrary file write vulnerability in Crawl4AI’s Docker API server, affecting all versions prior to 0.8.8. The flaw exists in the /screenshot and /pdf REST API endpoints, where insufficient validation of the output_path parameter allows unauthenticated remote attackers to write files outside the intended directory via symlink following and Time-of-Check-Time-of-Use (TOCTOU) race conditions. The vulnerability scores 9.2 (Critical) under CVSS 4.0 and can escalate to remote code execution on systems where the runtime user has write access to executable paths or cron locations.

Technical details

  • Root cause: Improper pathname validation (CWE-22) and unsafe symlink resolution (CWE-59) in the output_path parameter handling of the /screenshot and /pdf Docker REST API endpoints
  • Trigger conditions: An attacker sends a crafted unauthenticated HTTP request to either vulnerable endpoint with a manipulated output_path value; full exploitation requires pre-placing a symlink and winning a TOCTOU race condition, making attack complexity High
  • Attack vector: Network-accessible with no authentication required — Crawl4AI’s Docker server exposes a REST API on default port 11235; versions prior to 0.8.8 do not enforce authentication by default
  • Impact: Arbitrary write of attacker-controlled content to any filesystem path accessible to the runtime process; on systems where that user has write access to executable directories or cron locations, this leads to remote code execution and full compromise of confidentiality, integrity, and availability

Affected software

  • Crawl4AI (PyPI): All versions prior to 0.8.8

Severity

  • CVSS v3.1 Base Score: 8.1 (High)
  • Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Mitigation and recommended actions

  • Immediate: Upgrade Crawl4AI to version 0.8.8 or later, which contains backward-compatible hardening fixes that address the path traversal and symlink vulnerabilities in the screenshot and PDF endpoints
  • Network mitigation: If immediate patching is not feasible, restrict access to the Crawl4AI Docker API port (default 11235) via firewall rules or network segmentation to block unauthenticated external requests

IONIX Status

The IONIX research team is tracking ongoing exploitation attempts and recommends immediate patching. Potentially affected assets are outlined in this post.

References

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