CVE-2026-53753

Crawl4AI: AST Sandbox Escape via gi_frame.f_back Chain - Pre-Auth RCE in Docker API

State: Published
Severity: 9.8 Critical
Published: Jun 23, 2026
Updated: Jun 23, 2026
Reserved: Jun 10, 2026

Description

Crawl4AI is an open-source LLM friendly web crawler & scraper. Prior to 0.8.7, the _safe_eval_expression() function in the computed fields feature uses an AST validator that only blocks attributes starting with underscore. Python generator and frame object attributes (gi_frame, f_back, f_builtins) do NOT start with underscore, enabling a complete sandbox escape to achieve arbitrary code execution. The attack requires no authentication (JWT disabled by default) and is triggered via POST /crawl with a crafted extraction schema. This vulnerability is fixed in 0.8.7.

Scores

CVSS	Score	Vector	Source
3.1	9.8 Critical	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H	GitHub_M

Weaknesses

CWE-94 Improper Control of Generation of Code ('Code Injection')
CWE-913 Improper Control of Dynamically-Managed Code Resources

Affected Products

Product	Versions
crawl4aiunclecode	< 0.8.7Affected

References

https://github.com/unclecode/crawl4ai/security/advisories/GHSA-qxjp-w3pj-48m7

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