CVE-2026-53753: unclecode Crawl4AI sandbox escape in _safe_eval_expression

CVE-2026-53753 · Severity: critical · CVSS 9.8 · Published 2026-06-23

Crawl4AI is an open-source tool used to crawl and scrape web content for use with Large Language Models (LLMs). A security flaw in its data extraction feature allows an unauthenticated attacker to bypass security restrictions and execute arbitrary commands on the server or within the Docker container. This could lead to a complete system takeover, unauthorized access to sensitive data, and the ability to modify or delete files.

Technologies: crawl4ai (PyPI). Vendors: PyPI.

Quick answers

Is CVE-2026-53753 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-53753 being exploited in the wild.
How severe is CVE-2026-53753?
Critical severity, with a CVSS score of 9.8, published 23 June 2026.
Which products and versions are affected?
crawl4ai (PyPI) <= 0.8.6, ECOSYSTEM:introduced=0,fixed=0.8.7.
Is there a fix for CVE-2026-53753?
Yes. crawl4ai (PyPI): upgrade to 0.8.7 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-53753 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-53753?
Check whether you run crawl4ai (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • crawl4ai (PyPI): upgrade to 0.8.7 or later
    pip install "crawl4ai>=0.8.7"

Technical details

A sandbox escape vulnerability exists in Crawl4AI's `_safe_eval_expression()` function within the computed fields feature. The Abstract Syntax Tree (AST) validator implemented to secure expressions only filtered attributes starting with an underscore. However, Python generator and frame object attributes such as `gi_frame`, `f_back`, and `f_builtins` do not start with underscores, allowing an attacker to traverse the frame chain to reach `__import__` and execute arbitrary system commands. The attack is reachable via a `POST /crawl` request using a crafted `JsonCssExtractionStrategy` schema. This vulnerability is fixed in version 0.8.7 by removing the use of `eval()` in the computed field expression path.

Affected products

  • unclecode crawl4ai < 0.8.7

Identifiers

  • CVE-2026-53753
  • GHSA-qxjp-w3pj-48m7
  • PYSEC-2026-319

Timeline

  • 2026-06-02: advisory: GitHub Security Advisory published
  • 2026-06-23: disclosed: NVD publication date
  • 2026-08-07: patched: Fixed in version 0.8.7

References

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