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CVE-2026-56264 – Arbitrary JavaScript Execution and SSRF – Crawl4AI before 0.8.7

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Summary

CVE-2026-56264 is a critical code injection vulnerability (CWE-94) affecting the Crawl4AI Docker API server in all versions prior to 0.8.7. The /execute_js endpoint accepts and executes arbitrary user-supplied JavaScript inside the server’s Chromium browser instance, which is launched with the --disable-web-security flag, eliminating cross-origin restrictions. With a CVSS 4.0 score of 9.2, unauthenticated remote attackers can exploit this to execute arbitrary JavaScript and perform server-side request forgery (SSRF) against internal services, cloud metadata endpoints, and Docker-networked hosts.

Technical details

  • Root cause: The /execute_js endpoint in the Crawl4AI Docker API server performs no input validation before executing caller-supplied JavaScript directly inside a server-side Chromium browser instance.
  • Compounding factor: The browser is launched with the --disable-web-security flag, which removes same-origin policy enforcement and cross-origin restrictions, allowing injected scripts to reach resources they would normally be blocked from accessing.
  • Attack vector: An unauthenticated attacker sends a crafted POST request to the /execute_js endpoint with a malicious JavaScript payload. No credentials are required — the Docker API server has authentication disabled by default (jwt_enabled: false).
  • Impact: Executed JavaScript can probe internal Docker-networked services, query cloud metadata endpoints such as 169.254.169.254 to harvest cloud credentials, and exfiltrate sensitive data, enabling SSRF and lateral movement within the host’s internal network.

Affected software

  • Crawl4AI (PyPI package crawl4ai) — all versions before 0.8.7 (versions 0.x through 0.8.6 inclusive)
  • Specifically affects deployments running the Crawl4AI Docker API server (default port 11235)

Severity

  • CVSS 4.0: 9.2 CRITICAL — CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
  • CVSS 3.1: 8.1 HIGH — 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 to Crawl4AI 0.8.7 or later. Version 0.8.7 disables the /execute_js endpoint by default (opt-in via the CRAWL4AI_EXECUTE_JS_ENABLED environment variable), removes --disable-web-security from the default browser arguments, and applies SSRF destination blocklisting across all API endpoints.
  • If immediate patching is not possible: Restrict network access to the Crawl4AI Docker API server (default port 11235) using firewall rules or network segmentation so it is not reachable from untrusted hosts. Do not expose the API server directly to the public internet.

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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